I have been having a problem with my 2005 Envoy 5.3 for over a year now. I get multiple codes including p0443, p1682, p1516, and p0689. I recently had my fill and paid a mechanic to come out and diagnose the rig. It started with intermittent stalling and after 20-30 min break would start again. Then went to intermittent starts setting off the reduced power trouble light. I replaced the throttle body and the map sensor which cleared up the throttle delay and reduced power light. Now it will start fine and run for exactly 37 min and just die. No start after that for at least 3hours. I'm losing my patience with this thing. Please help me figure this thing out. I've started this thing several times today and it runs great for 35-40 minutes then falls flat on it's face. Any ideas about repairs would be greatly appreciated.