I've done most of the tune-up things suggested, but still wasn't satisfied. I pulled all the plugs and injector connectors to check my compression and noticed that my plugs looked dry with some carbon indicating a slightly rich condition, but that on the threads and ABOVE the gasket they were wet. And, the plug holes had gunk and oil coating them, especially where the gaskets were supposed to seal.

I cleaned all the plug holes out until they shone, and then checked my compression - 180-185 across the board, which I think means I've got carbon buildup, but that the seals and rings are fine.

Cleaned the plugs, oiled the threads a little, then put them back in and torqued them to spec. Squirted contact cleaner on the injector connectors and reinstalled. Took it for a drive - WOW. I don't know if the plug gaskets couldn't seal against all that gunk or what, but it's like a different car.

Moral of the story - check and clean the plug threads and gasket seating surfaces if you're tuning up a car. Don't just stick in a new set of plugs. I hadn't seen this mentioned anywhere, pretty obvious in hindsight.

I also put 195/60-14s on it, which means it now looks like a go-kart, but it also accelerates and corners like one.

Hope everyone had a good holiday season, back to the grind...

 

what color was the carbon? gray is pretty much normal but black is no good, and they should be dry

did you see moisture around the plug holes?

 

Yeah, it was black - so the seals and rings may still be no good and there's just so much carbon in there it's making the chamber smaller, raising the compression - but all the readings were consistent. And I know it runs rich.

There was plenty of oily moisture around the plug holes. I'm gonna monitor it and see if my oil loss gets any better, and if the plug holes stay dry now that the seals are good.