P0401, two shops and the Buick dealer cannot cure code.

What is your question?

All systems work correctly, all measures and voltage within specs. No clogs, no vacuum leaks, pintle opens and engines shuts off at idle, no cracked hard lines. Dealer cannot find problem and now wants to remove lower intake to find what they cannot understand. Car runs excellent, fuel mileage great, no stalling, missing, no problems. CEL will not stay off after resetting. I believe the dealer is fishing for funds without a clue. Should I allow removal? What are they missing? All information appreciated.