Before I posted this successful result (no more P0172 and P0175 errors) I made sure that it was a valid fix.

I do not not use my own scanner... I go to a local auto shop and use their scanner... I do not get the BMW codes but do get the OBD P-codes and have the Bentley service manual to interpret them.

After my fix (replacing the missing gasket on the throttle valve side of the mass air flow sensor) I had the error codes cleared, then drove around sufficiently that if the problem remained, the codes would have reappeared.

So... no more engine light after sufficient driving... I call that fixed. Interesting that a missing gasket and resulting reduced air flow past the mass air flow sensor can result in the P0172 and P0175 errors.