After another AMM replacement, I must publicly state my contention that the AMM (and not the A/C evaporator, despite its central location) is the heart of every brick out there. It was so on my 740 (and if you have a decent used B230F, let's talk. This box has 325K plus and is TIRED) and it's so on my 240.
The latest on the 240: Check Engine light, ECU codes indicating both too rich AND too lean. Spotty cold idle from time to time, with occasional stall when engaging drive - bogging down when initial load was applied. Naturally, I suspected the mass meter. It's the classic 'idles poorly, runs ok at speed' situation. Replaced the AMM this weekend and voila! Smooooooth idle and starts up without even a thought of a throttle touch. Drops into gear with no problem...

Note that I experienced hunting at idle for the first 15 minutes or so of operation after AMM replacement. I attribute this (correctly, I hope)to the ECU finding the new setpoint for its outputs.