just came across one of my notes from when i was working at the dealership back in '00 and '01. while i was there, i did a little upgrading to my C1500 5.0 TBI. i upgraded to a full 3" exhaust system from a 5.7 truck. the 1 ton trucks had all the same exhaust, except for one minor difference... no cat. instead they had a straight section of pipe there, with the proper flanges to bolt directly into the place of the cat. i bought one, and it worked great. thought you guys might like the info. probably alot cheaper than having an exhaust shop make you a "test pipe", at only about $20. the GM part number is 15522374.