I have a 02 Envoy that I just bought. We thought the Timing Chain was out, so tore it down and it's right on. It keep throwing a P1345 code, we even took it to the dealership to have it scanned and it still comes up with the code. Put a new Acuator on, and have done the regular stuff. It runs great, until you put you foot into it, and it falls on its face. No guts at all. Could it be a plugged CAT, doing this? If you slowly build up speed it's better, but it revs high, then if you take your foot off the gas for a second and then put it down, it shifts and the revs come down.