I've got a 4 speed with a 2.5" system on it, the sound of it is more or less the same as a manual with the same thing, don't know why u would think it would sound different. I've got a 2.5" cat 1 muffler and 2.5" pipe goin all the way to the end, I noticed a slight increase in power, very slight, but that woulda been cos the old catalytic converter was ****ed. cost was $380 fully installed, a stock system costs $440.
I also have an aftermarket shifter on mine, it feels a hell of a alot better than the shitty stock thing. Cost me $30 from repco but it was a shitty blue with black checks on it. I just finished sanding it back and spraying it the same colour as the car so it looks real sweet now, the only bad thing about these aftermarket shifters is that you gotta sorta drill holes or put indents on the shifting rod thing so the grub screws have somethin to hold into, takes a while to get it configured properly. and if you ever sell the car and put the old shifter back on there are gonna be marks on the shift rod thing from the grub screws
Phat Drift Damaged
Cobalt Blue 1994 EF XR8 5 spd
Fully optioned - Sunroof, cruise, body kit
Stock as a Rock for the moment