I think kenton is on the right track...you either need to
1. Be happy with your car,
2. Do a bunch of research before asking more about internals, etc, or
3. Get a different car.

If it was me, and you don't have the budget for a new car, but want yours to perform better...I'd forget about straight line acceleration because no matter what you do, unless you have $5-10K or so, it's still going to be slow.

Instead, put your money into quality sticky tires, quality suspension upgrades. Having a good handling car is the first priority for me. If you get the car handling great, you decide you want to go all out and do engine mods, go for it.