Save yourself a headache. Buy an sct x4 and get with shaun at AED or palm beach dyno. If you buy that silly tuner from livernois, you're stuck with them as no one else tunes on that 80s looking platform. I like options.
I'd hold off on any type of shorties, the stock "manifolds" are pretty good. The cats are the bottleneck on the stock system. I'd hold off until you are ready to go with long tubes.
i don't work for AED. I just fortunate enough to have him for tuning services / advice. Use google, you'll see Shaun is one of the most IF NOT the most stand up guy in the coyote community. I can guarantee you there is no bias or shenanigans with his testing.
like bj stang said. airaid / mishimoto elbow, velossa tech ram air and a good panel filter (green, afe, etc..) will be hard to beat. no tuning required as well.