Man, Its been only since Christmas I put on my whole new exhaust system and its leaking. Well, At the moment I am unsure of whats wrong since I cannot raise the car. At the moment I am assuming that my y-pipe has holes and is damaged. I just recently changed my oil and found a bolt jammed between the K-member and the y-pipe. I got the bolt out and apparently left a dent in the pipe When I installed the exhaust I didnt exactly have everything I needed to seal off from the y-pipe to the cat. Which leads me to something else, on my dad's truck he had the same problem. Since he is a crane design engineer he designed a y-pipe on his own, that got rid of the cat and bolted directly on his exhaust. Exhaust shops do not allow custom y-pipes installed at the shops if they knew of the cat was going to be gone, so they just designed it for him. Just let them assume or know that it will bolt onto a cat

Looks like if this is my case, I will probably do the same thing. I have the MAC headers and Flowmaster American Thunder exhaust. I am thinking of having the diameter of the y-pipe increased from 2.5" to 3". Can anyone tell me if they have done this and felt any gains? Will post how the exhaust looks later.