OK, here's the story,

Factory rebuilt, normal ported engine with about 625 on it, and turbos with about 9,000 on them. Started up fine (normal 2.5-3k spike, then to idle,) ran fine, normal spooling response (10-8-10,) until I got off the freeway. Then the car started having power surges. It would bounce between 1.5-3k while at a stop. Pulling about -20 on the vacuum at the same time. What blew off/got stuck/broke?

 

If your pulling a constant -20 on vacuum, you may be looking at a cracked seal. But I doubt it considering -20 on vacuum is good.

 

Well, checked the throttle body, and it was clean. I never managed to get to the EGR system. But somehow, some way, it corrected itself! This leads me to belive that it was a stuck EGR valve that got stuck when I went through the initial turbo warmup (10-8-10 in third gear.) I was going to take a huge (60cc) syringe, pull of the vacuum hose running the bloody thing, and gently persuade it with air. It took some driving in the driver friendly DC beltway (riiiiight!) to knock it back into operation. I would still replace the EGR, but:

1. It can wait until after I am done with my next business trip.

2. It is not an emergency replacement now.