Im getting a 5 spd 1986 mustang gt, what would be some good performance upgrades for it?
The 86 is the first year of the sequential fuel injection. It also has flat top piston with bigger combusion chambers (not the best head) also that version of FI does not like much cam (the lope at idle you talk of) with out getting pissy (rolling idle, etc) I would get it first shake it out to see what is worn out first before replacing good parts. But if it is a 5 spd, put a set of 3.55 gears in it and maybe some flowmaster 40s.(maybe a little loud) Make sure your timing is set good. Mabye a base of 11-12. Maybe replace or loose the cats if they are still there, Make sure the air intake silencer is removed from the inner fender. Don't go spending stupid money on things like cold air intakes or different shorty headers until you just get the base line solid and better rear gears. That may be enough for you. Have fun!!