Found a BAC at a junk yard and compared, can't see much difference in the operation between that one and mine. I'm gonna assume it's fine.

Also checked my vacuum rack and found no clogging anywhere.

Only things left: new fuel pressure regulator, new airflow meter, and a different ECU.

If those don't fix it, then maybe I'll start offering money to whoever can figure it out.

 

Ok, got new fuel pressure regulator and found a spare ECU, made no difference. Fuel pressure measures about the same as with old fuel pressure regulator. Still refuses to idle above 300, and idles horribly rough. Mind you when I drive it, it drives ok. Only when I let it idle does it completely bog down.

I actually checked vacuum at idle, and it's at about 14-15. Could that be it? I know the engine isn't broken in yet, so compression is going to be crap... But last I checked it was high enough, just not even.

Also with my new FPR when I turn the car off, fuel pressure goes to zero almost immediately. WTF?

I don't know what else to try.