I just recently picked up my first GT Mustang and I must say that now that I finally have one, I feel my life is almost complete. The question I have is that I had a complete flowmaster cat back installed with the 2 1/2 in flow tubes, and all was good until about the second or third time I started it up. When I did, it sounded like a "clunking" sound in my muffler and my car kind of shook for a second. Since then it starts up smooth, but from time to time I get the rough shaking start-up. Could it be that my cat's were clogged up and it is just blowing whatever it is blocking it out, or could I have some type of leak somewhere. I am going to replace all the cat's in a few weeks any way with a mac o/r H so maybe that will be the difference I'm looking for. Sorry if this sounds confusing, but I didn't know how else to describe it. Thanks in advance guys!
Brandon
Brandon