Some of the things I have done with my V6:
JBA True H Dual Exhaust - $750
JBA Titanium Shorty Headers - $500
JLT True Cold Air Intake and SCT X3 Tuner - $725

 

This really worth it? Does it kill your gas mileage?

 

Yes, it is, and no, it doesn't -- seems to cost about 3mpg on the highway, and I'm actually gained 5mpg in town, because I can cruise around at 35mph in 5th gear with the cruise control on

The one problem - if you go for a droney exhaust system, cruising on the highway with 3.73s tends to put your revs right in the heart of droneland, and it's just awful.

But a GT muffler is drone-free, as are the Corsas, and both sound great on a V6. Trac-Lok and 3.73s = major major MAJOR difference in the fun factor. #2 best mod I've done.

But you NEED a Trac-Lok. Trac-Lok and stock gears is still a vast improvement over the stock open diff.