As far as exhaust go, your choices are 1) custom:you pick the muffler, and pay for the piping, welding, and decide your own sizes. It is definatley the most cost effective way to go, but keep this in mind...why do you think people make fun of Honda's and their COFFEE CAN MUFFLERS???. 2)Cat-back: name says it all. It is designed to maximize exhaust flow, and they are application specific. As in, turbo only, not for the MP3...They are pricey($500-700 normally), but they are tuned just the right way. 3) A rear section muffler(if they make them for the MSP) Basically, an exhaust that bolts up to your stock piping, usually somewhere around the rear strut area. It can run fine off your stock pipe. Usually about $300