Sounds like the car has a few issues. I would work on sorting those out before any mods. Worst thing you can do is dump all your money on toys and have something fail on the car that is a basic need. Start with fluid flushes, all your tune up adjustments, etc. Not near as fun sounding but, performance parts are only going to make things worse if you don't have a good foundation. Coming from the Gen 4 world, no one likes dropping $1000 here and a $1000 there for fluids, fuel pumps, coolers, exhaust, etc. However, once you get those in for a good foundation, the tuners can really open up and start making power. Each part builds on the other and if your foundation is stronger and not being forced to run on the ragged edge, when you add the performance, you will have more reliability and more power.