I have a 2.5" diameter cat-back exhaust. I am looking to upgrade to a 2.5" diameter high-flow cat and DC Sports header. What is the diameter of the header pipe that connects to the cat? Will it bolt up to a 2.5" cat or will modifications have to be made? Also, DC doesn't come with new bolts. Does anyone has a listing of bolt sizes so I can buy them before replacing the header?