Sounds like we have the same problem.Did you ever get to the bottom of it? I read a post somewhere, though I can't find it now, that said disconnect the speedo. I did, and the problem almost went away. Almost, it's still there but not nearly as bad. It's still under powered and very slow on the hills.I have cleaned the inlet manifold and changed the MAF sensor so far but no joy. Has anybody discovered the remedy for what seems like a common problem?