The high flow sounds like the best Idea easy to install and comes with a bung. I have a megan racing one on mine. I got it off ebay and fits good no extra modification needed. thats only if your gona mess around with the cat or not, other wise just let it be. have you thought about upgradeing the exhaust to a 2.5 or a 3 inch setup? you could go with a long tube header and go from there.

 

I only want to increase the performance to get a little better gas mileage, not to try and run the hell out of it. It is a 98 auto trans with 63k on it. I run around a big city a lot...I have a 05 Ram 1500 with a hemi, I like the ease of zipping around in the neon noodle.

 

Weight reduction and skinnier tires are the easiest way to improve gas milage.

 

Yeah the rims and tires help out, keeping it tuned up helps too, if you like zipping your neon around you should look into those rims and tires and maybe a sway bar.