Ok, I ordered a valve/solenoid from Autohaus and lost my confidence in changing it myself. (If I had a second car, I'd have tried it - been without a second car for over a year now.)

Anyway, they changed it, it was not plugged at all. Dirty, but not bad at all. The little plastic part that the solenoid moves to allow the vacuum to operate the valve was bad - mechanic says it looks like heat did it and I agree. They have seen a lot of Mercedes do this in the past.

He also said that the PTCM uses the MAP reading to determine if the EGR is opening or not in the Crossfire and it's Mercedes siblings.

Anyway, he cancelled the code, no light now and no beeping from the UltraGauge. $128 for labor and $12 for the gasket.

Glover's garage in Cumming, Georgia sure seems to know the Crossfire. (I saw two Mercedes in the yard there today, and one partner's wife drives an SLK with something like 170,000 on it.)