That's what you are going to find with most engine mods. It's not really worth it IMO. If you want to increase the performance, spend money on the suspension and tires.

If you really want speed, you could check out the Comptech supercharger, but with your car, the limiting factor in performance will be the auto tranny. They don't handle more power than stock very well from what I hear.

If money is tight, you could try nitrous for the occasional fun.