Barry,

Wow. You have every right to hate that car.

Have you tested the operation of the 02 sensor with a multimeter to see if it detects lean and rich conditions? If the car is running very rich or very hot, the new sensor you put in could have been ruined. I know, happy thought. And you put in the right sensor, right? Reginas take a totally different O2 sensor than the Bosch cars. I'm not suggesting it is the root cause of your evils, just that as you try to track down the main problem, you keep an eye on that sensor b/c it might be toast by the time you're done.

There was no visual dirt/corrosion on my multiplugs either, but I sprayed them with tuner cleaner, polished them w/ 600 grit sandpaper, and then sprayed them w/ De-Ox-It anyway. Figured "while I'm here, might as well" and it appears to have solved my problem.

Are you sure the timing belt isn't off a tooth? Obviously it was doing this before you pulled the head to do the gasket and is still doing it now, but were you absolutely certain things were all lined up correctly? One tooth off and the car will run, just poorly.

When the head was off, what did the exhaust valves look like? Did you have any head refurbishing done? If things are getting that hot on the exhaust side, I'd be worried about burned valves and shot valve guides. Again, not a root cause but could be a major contributing factor to the extra-crappy running at this point.

John