[finall]

Ok, I have now crawled under the vehicle.

YES!!!! The crossover exhaust pipe (going from right side to left side collector) is totally pancaked against the UCP (undercarriage protector). GM tried to pancake the exhaust pipe so it would clear, but failed. I had to drop the back of the UCP bolts by 1/2" before the exhaust cleared.

The rub point has filed down the UCP at the contact point and exhaust pipe also. If this was left alone, it would have eventually made a hole in the stock exhaust and UCP!

Lots of loose metal rust filings in the area, so it was easy to spot. I could not even slip 1 piece of paper between the two pieces of metal. Could this be the problem? Either way its off to the dealer to fix the exhaust.

I easily removed the UCP (3 bolts) by loosening the front skid plate (5 bolts), and will go for a 50 mile test drive later today. Let's just hope that this is the problem. Either way, it is off the the dealer for warranty exhaust repair.

AdamInCo: you may be the Hummer God after all......More to follow.