As far as exhaust, I would stick with a 3" DP (fullrace, skunk2, ultimate racing, etc.). I've read that ~90% of the power gains with a good tune comes from the DP, the other 2 ~5% is from intake and exhaust.
As for coilovers, it was recommended to me by a reliable source who tracks and races their 9th gen, to get GodSpeed Monomaxx coilovers. I was skeptical at first because of the price, but was reassured that these things were great. I've put around 8k miles on them, both on the streets and small tracks and they've been incredible, especially for the price. Granted, the vendor could've upsold me more expensive coilovers (I was actually looking to spend over 1000 for coilovers), but they guaranteed their quality and longevity. They do have a higher springs rate of 10k front and 14k rear.