Two problems related to engine exhaust system have been reported for the 2008 GMC Envoy. The most recently reported issues are listed below.
2008 GMC Envoy 51,000 miles exhaust manifold cracked I had it replaced and was told by dealer a 3 day wait would be necessary as they had used stock parts on another Envoy with same problem . Advised me not to drive because it may catch fire.
Bought the vehicle last November from georgian pontiac Buick GMC in barrie ontario canada last November 2009. Learned I had a cracked exhaust manifold on my 2008 Envoy at 87 000 km. It has not yet been repaired. Research is ongoing.