The exhaust isn't very restrictive in those cars at all... All your power is to be found in the heads and intake manifolds
Your best bet is to go with some gears.. I put 3.73's in my 95 Gt auto and they are just right for me... But I also do a good bit of highway driving....
Or just save your money up and do a H/C/I swap....
This summer im going to throw some afr 185's and a new MAF/injectors and a larger cam in mine
Don't expect large gains from anything until you upgrade those heads

Trust me... i've done them all and i'm still running stock heads
I'd say out of my list the best mods are the shift kit and the gears....
