I'm really starting to get worried now. When I did my last oil change, my VX had burned off quite a bit more than usual, and over the past month or two it's started to ping and lose some of its power. I've been frantically doing everything I can think of to get her back into shape (including changing all my fluids, cleaning out the air filter, changing the spark plugs, etc) but I'm running out of things to do and the performance hasn't improved much. Switching to higher octane (89) seems to have helped the pinging a bit, but I ran 87 octane for the first 70k miles without a problem, so something has definately changed.

Someone suggested that carbon buildup could be the cause, and I read in another thread that the PCV and EGR valves could get clogged and cause premature engine failure. Could this possibly be the cause? Does anyone else have any suggestions for what might prevent this type of problem?