Exhaust upgrades
If you have the $$ get some stainless steel, Kooks or QTP are the ones most frequently mentioned
http://www.lmperformance.com/4612/1.html
Do cats help with gas mileage or just emissions? No cats would make the exhuast much louder right?
Macs are a pretty good header, but if you're planning on more serious mods, you should really go for the long tubes (if you aren't macs will do fine (not alot of difference between them and LTs)

