I have my main cat out and was going to install my test pipe. Thing is the dumb ebay listing said it was 12.5"s and it is actually 15". I was wondering how I would be able to tell if my main cat is good or bad by looking at it. I can see light thru it and very little of the honey comb is closed up. May be dirt but I am not sure. I either have to have this test pipe cut and rewelded to the proper length or have a stud removed from the original cat(I had to cut one of the studs off as it did not want to come off).
Thanks!