Mega, Im going to hold the throttle lever in place to rule that out. In fact, im gonna hold some of the other linkages in place.....interesting thought. Ill clean and regrease them to make sure they work as advertised.

Liquid...I have replace the usual suspects you mentioned with MB parts or good working parts from a loaner 16v.

Today I swapped out the coolant temp sensor, coldstart valve and fuel pressure regulator from a known working car. Symptoms improved but still hunts from 900 to 1100 when warm and drops down to 500 briefly on a sudden throttle let off. Combine a throttle let off with a sudden turn, and it will stall..30% of the time. If I load up the motor (lights, heater blower and tuning the wheels) with a throttle let off, It dies 60% of the time. Not as bad as before the new loaner parts.

The timing is dead on, I rechecked everything. Im going to burp the coolant system.....thinkng that air bubbles might be throwing off the coolant temp sensor thus sending a bad input to the ECU. I might also swap out the 02 sensor with the one that came with the car....Im running a generic Bosch 3 wire unit.

After I swapped the parts today, It idled perfectly at temp until I blipped the throttle, then surging.

Im off for training next week but will attack it after the 15th. I might bite the bullet and take it to the local guru IE throwing in the towel. Man card revoked.

Edit: seeming how the surging is only when warm......failing cat?