2001 Eldorado stalls after start, no relevant codes
 

Northstar 4.6L , 130K miles. Stalls after start a half dozen times before finally staying running. Only semi-relevant code is P0507, high idle detected - that was a problem a few months ago, cleared itself.

What I have done:
Cleaned MAF sensor screen, cleaned throttle body (it wasn't really too dirty).
Looked for vacuum line breaks, sloppy connectors, etc - did't find any.
Checked air filter, clean, and the air filter housing is properly closed.
Threw a few cans of SeaFoam in the tank, ran the tank down, refilled, one more can, no help.

Any ideas?
thanks
Art