For performance go for denso iridium spark plugs (IK20) or (IK22) if you have a supercharger. These cost for these is about $70. Try a cold air intake, you can make a custom one or I think Injen makes them for about $225. DO NOT get a short air or ram air intake, they almost look the same as the cold air intake but they will TAKE IN HOT AIR in the summer and negate the fact that you have better air flow so stay away from those. Definately get a TRD drop in air filter or a K&N one for about $60 if you would rather keep the stock air box which is cheaper and not a bad idea. If you have the cash, get a TRD S/C for around $2000 on ebay. Don't get exhuast unless you plan on having major mods done. CATTMAN is currently developing headers and y-pipe for our cars, these would be great mods for air flow, but not too sure on how expensive they will be. Look out for those later this year. If you plan on spending a lot of money and getting major mods done and if you have any complex questions check out Teamsc3.com's forum their members have more knowledge than I do. For suspension try Tokico performance struts. They might run $340 on ebay. Do not get TRD struts as they have knocking problems and were discontiued and can't be replaced. And lowering springs. Go with Eibach or TRD. You have the right idea with the TRD Rear sway bar.