I can try that. I am just confused why when I unplug the TPS or even the MAF the pinging stops as well - even though those items are not the cause of the problem, since they've been replaced.

AirCare technicians talk about carbon being very stubborn to get rid of. Here's an alternative to the Seafoam procedure outlined on this board. It comes from "AirCare Repair: The Emissions Repair Advisor".
I've made a few changes to be specific for the Panther platform.
a) Allow the engine to run at idle for 10 to 15 minutes before adding TEC (Top Engine Cleaner or equivalent (Seafoam)) TEC is no longer made, according to the parts counter guy.

b) Remove the air cleaner
c) Remove the MAF connector (put the computer in open loop)
d) Pour half a can of Seafoam into the throttle body at a slow, steady rate with the engine idling.
e) Pour the remaining half can into the throttle body* at a fast enough rate to stall the engine. Let Seafoam soak in the engine a mininum of 8 hours.**
f) Start the engine and idle 10 to 15 minutes. (Or drive 10-15 km at night so the local fire dept doesn't think you have an engine fire! If the Seafoam was dumped in properly, it will smoke.
g) When back home, idle the engine at 2000 rpm, pour another can of Seafoam into the throttle body at a slow, steady rate so the engine does not stall.
h) With the engine at 2000 rpm, at a slow steady rate so the engine does not stall, ppour two quarts of water through the throttle body to decarbon the piston faces and the valves in the cylinder heads.
i) change your oil.
j) check your plugs.
k) verify correct O2 sensor operation.

"Combustion Chamber Cleaning", AirCare Repair: The Emmissions Repair Advisor, 1997 #4. Retyped with changes reflecting the Panther.

* Pouring the Seafoam through the throttle body seems to make a difference. Both my father and I have tried it through the PVC valve and noticed marginal improvement. We then tried adding through the throttle body and noticed better results.

** the soak time appears to be critical. You can wait longer, but don't skimp on the 8 hours.

I tried the Seafoam method outlined on this board and elsewhere. It would improve things, but not perfect. I performed this treatment in the past and I did notice better performance. The pinging and hesitation just before 4-3 and 3-2 downshifts was virtually eliminated.

Also, one service tech had tried MotorVac and it did not solve the carbon problem. The above procedure then did correct the carbon problem.

one of the EGR benefit is supposed to cool down combustion chamber lowering down pinging issues... don't ask me why tho...!

because exaust is an inert gas (means cannot be burnt) so if you add a gass that cannot be burt it helps keep the combustion chambor temps down which helps with nox and pinging issues

Yes, but if the pinging is under load only, the EGR valve is shut so this wouldn't be the issue. So far as unplugging the maf or tp correcting the problem, any time one of the critical sensors involved with air/fuel/timing management are unplugged/open circuit, the pcm will run on a default strategy since it is blind in one of the important aspects and will always be in a "safe" management strategy which will usually include less timing and more fuel. Rich is safe! I'm almost willing to bet that it is severe carbon build up with all that you've stated so far, seeing how it is decent mileage and all of these have a problem with pulling in oil vapor which causes the problem...more so on fleet vehicles that tend to go long on maintenance intervals and cop cars are real bad about idle hours not showing on the odometer, which means longer run time with the engine oil broken down which aids to oil vaporization and ingestion through the pcv valve hose and crankcase breather hose on the other valve cover. Enslow's write-up about a good top-end cleaning is detailed and would help the concern. We used to do the same with the Motorcraft spray carburetor cleaner (foamy kind). Must do it with the motor good and hot and let soak in. Water, as long as it's not in heavy volume since hydro-locking the engine is a BAD thing, is a great de-carbon agent. Good luck!

Yes, but if the pinging is under load only, the EGR valve is shut so this wouldn't be the issue. So far as unplugging the maf or tp correcting the problem, any time one of the critical sensors involved with air/fuel/timing management are unplugged/open circuit, the pcm will run on a default strategy since it is blind in one of the important aspects and will always be in a "safe" management strategy which will usually include less timing and more fuel. Rich is safe! I'm almost willing to bet that it is severe carbon build up with all that you've stated so far, seeing how it is decent mileage and all of these have a problem with pulling in oil vapor which causes the problem...more so on fleet vehicles that tend to go long on maintenance intervals and cop cars are real bad about idle hours not showing on the odometer, which means longer run time with the engine oil broken down which aids to oil vaporization and ingestion through the pcv valve hose and crankcase breather hose on the other valve cover. Enslow's write-up about a good top-end cleaning is detailed and would help the concern. We used to do the same with the Motorcraft spray carburetor cleaner (foamy kind). Must do it with the motor good and hot and let soak in. Water, as long as it's not in heavy volume since hydro-locking the engine is a BAD thing, is a great de-carbon agent. Just be careful with how much raw liquid of any kind you use since the intake on a 4.6L has a low belly in the valley that tends to hold these liquids (including oil) and takes some time to get to burn out of there. If using a combustible like Seafoam or other cleaners, it will cause driveability issues and rich codes until it is gone. Won't hurt anything, just may be misleading or set a check engine light until it burns off. Long, higway runs with WOT accellerations usually do the trick. Good luck.

A note on using water after the Seafoam:

I used to be scared to add water because of the fear of hydrolocking. When I saw that I was to add 2 qts of water, I realized that I could a steady thin stream of water. I was safely able to pour the water in a thin stream into a funnel. The car seemed to run well after and I was going to shut it off and leave it, but I decided to give it a test run. I'm glad I did because it did stumble a little in the first block, and blew out more white smoke. I suspect the reason for this is there was some remaining loosened carbon in the intake, and perhaps some pooled water in the belly of the valley.

Do be careful when adding the water, but pouring a steady thin stream directly into the TB, followed by a test drive seemed to work.

ideas:
1-adding water "thin stream is a great safe idea", my idea is to let the stream to flow for a longer time into the engine (driving or idling) but not to let it stall .
2-water vapor is more useful to do the job, but we need a constant vapor source.

here we have some question: how is it bad on the cats when letting the thin stream water to flow into the engine? let say 2-3 quarts for 30 minutes driving for example?

As far as the cats are concerned water is one of the products of combusting the unburnt hydrocarbons. Water will NOT hurt the cats in any way.

Stalag

Did the dealer mention anything about monitoring TPS and MAF voltage?

No. They just said "everything you can check with a computer says there is nothing wrong" and they also said they tested a new MAF.

So atm. I'm looking at doing some intense carbon busting to try and stop pinging.

As for the bad bucking/hesitation, anyone know how I can test the TC? Remember, it only happens when I accelerate hard and I am already rolling.

The bucking/hesitation is often a symptom of carbon buildup. One technician explained to me the bucking I felt was known as a "lean miss". The mixture has too much oxygen for the given temperatures and compression, and the mixture doesn't burn properly causing a miss.

I usually experience the bucking just before the 4/3 or 3/2 downshift, especially coming out of TC lockup. After decarbonizing, the bucking goes away.

Big relief if the bucking/hesitation is just from carbon.

I'll let everyone know how my carbon removal efforts go!

any luck? howd things turn out

Don't worry, I still have intentions of posting my progress.

It's just that so far, I haven't had any more yet. I've done two full cans of Seafoam that seemed to help at first but the pinging has now come back. Guess I'll have to check fuel pressures next.