Hey everyone, I'm new here & hoping someone out there can give us some advice. My brother just bought a clean low mile (40,000) '06 TB. It started missing a few days ago, so I did some troubleshooting and found the #5 cylinder is not firing. I talked to the local Chevy dealer about the problem, he said he had heard of the valve seats coming loose and hanging the valve open. I did a compression test and sure 'nuf, #5 had no comp. The engine ran great up till this point and made no noise at all. Has anyone heard of this happening or any thing else that might cause this. Any sugestions would help greatly being it is out of warranty.