you could free up some horsepower and lower end torque by investing in headers, a high flow cat, and a cat back exhaust system. i recomend getting name brand stuff, Apex'i, Greedy, HKS, DC sports and so on to get the max amt of power in this area. even though your gonna pay more these parts are tested and have been proven to add more hp than no names off ebay. Also theyll give you a better sounding exhaust system which prob wont fart or make your car sound like a weed wacker. anywayz just make sure you do alot of research before buying anything and look around to make sure you get a good deal