8.1 Vortec

107k miles on my 02 no problems

A common problem on them,I had 4 sets replaced all under warranty.

If it is fairly new it may be covered. They made some new models with a cut between each exhaust ports that seemed to work for awhile. The other fix was to put headers on,not an option here in California due to smog regulations.

I was told by my RV mechanic that it was more common on RVs than in other applications is because of the limited air flow around the engine,the 8.1 runs very hot exhaust temps tending to warp the manifold.

Mine is fine at 73K miles. My brother has the same engine on an older Yukon, no problems as far as I know.

Yes; several have reported so.