Not trying to send you on any sort of wild goose chase; I have just been dealing with a similar situation. I explained my situation here: http://www.grandprixforums.net/threa...e-Knock-et-al)

I ended up buy a really cheap usb inspection camera on amazon and discovered I had a chipped piston. I would go through all of the other tuning ideas first, but I ended up at my wits end with it.

Good luck.