i just did the same swap i got my exhaust off of ebay 2.5 all the way back for about 200$$ i have a itr header and bought a 2.5inch hi flow cat had the exhaust shop weld the cat in for about 150 and im very pleased withthe way it sounds it was a little loud for me at first but the exhaust came with a silencer and i put that in and am very satisfied with it