Hey guys been a while since I been here but I acquired an 86 MGM box again so here I am. I am trying to fix the hissing noise that is pretty common on these cars. I know the remedies to fix it, but I'm having trouble finding where this vacuum line is located. Is it under the hood, or am I suppose to be looking inside the dash by the gas pedal cause between the pedals there is a white line but I didn't want to mess with this until I know what I'm doing and to be honest right now I don't feel like I am. If someone could send me a pic of where this line is it would help even more I feel like an idiot but under the hood ther's so much junk under there I can't tell where I'm suppose to be looking. Also the gear shifter requires a bit of force to get it to move my old GM had this same issue would it help to spray some lubricant inside the gear selector slot thing? Thanks guys.

Under the dash near the parking brake.

https://www.crownvic.net/ubbthreads/ubbthreads.php?ubb=showflat&Number=79283

I've always just disconnected and plugged the white vacuum line that comes thru the firewall and runs to the vacuum switch that is on the shifter linkage on the column. You could disconnect it at the parking brake, but then you still have vacuum at the vacuum switch which is potentially leaky, so just eliminate the vacuum supply for the whole thing. Did this to my buddy's '88 and '91, and I want to say I did this on an Aero too but honestly can't remember if it was one of mine or his, its the same basic system on any year that had it aside from the vacuum switch being different for the different columns ('79-'89, '90-'04, and '05+).