Chips on ebay will not work. You can spend $1000 or more on a full headerback exhaust for 5-10HP. Not worth it.
If you're sticking NA, it's better off to do a 2.5 engine swap. They can be had for relatively cheap and you'll be getting a +30 HP gain right off the bat before an exhaust or cams if you go that far.
Or you can sell the car and buy something faster
that's always the best option if you have the $$$