I was looking to keep my 2.5" down pipes and exhaust. It wasn't too long after that I went with 3" down pipes to 3" exhaust. And before it was over I ended up getting GTX2863 turbos, new 5 bolt 3" down pipes and new exhaust. Best place to start is your end point if that makes sense. It will save you a lot of money! If you are looking for a little additional HP either of those turbos are good. I also think the GT600 are 4 bolt exhaust. Good luck with your quest