I have done everything you have mentioned in your post. Gone through the factory CD trouble shooting matrix a few times. Checked the compression and leakdown numbers, yes the first stroke is important and telling. Checked fuel pressures, upper and lower chamers, and residual pressure. Replaced anything questionable, including a few good parts. Adjusted the valves, resealed the whole intake system and reset the resting height of the air flow meter. Lamba is in spec and fluctuates at temps.
It starts on the first turn of the key when cold......and stalls or almost stalls when hot. Air flow meter is in spec with no open circuit noted while driving around the neighborhhod.
My neighbor, who owns his own shop and has worked on MB`s, BMW`s and Porsches for over 40 years is also stumped.
I am searching for some new ideas......