I brought a car into our shop to begin conversion to a 944 spec car but it has an engine issues. This has a hard start, stumbles, but will run flawlessly at 2000 rpm and over. I ran resistant tests on all the sensors, replaced a defective crank sensor, cleaned all the injectors and even swapped out the computer to eliminate that. It is a 1984 model and this is the problem the previous owner encounted during his last HPDE events. The second you go into the key on / start mode the engine will fire and die. this is repeatable over and over. If you give it throttle it will run, and run well but will not continue running if you don't hold the throttle to keep it running at the before mentioned 2000 rpm. I also had a spare air flow sensor and swapping it made no difference.
All 4 cylinders carry 175 to 180lbs of compression and there are no apparent vacuum leaks.I did verify the timing belt alignment and it is dead on. Where do I go from here? Thanks, Mike

Check or swap the AFM.

That was done,I called it the air flow sensor but I swapped the entire unit, I suppose I could have 2 bad ones but I will run the diagnostic from Clark's garage. Thanks

It suggests a problem with vacuum leak, I'd check the operation of the aux air valve, and the idle position switch...

Bench tested the AFM, not the problem. Is there a test or bypass procedure on the aux air?

I would double check for any vacuum leaks after the throttle body, loose hoses or a split in the J boot, the easiest way to check the ISV is to simply pinch the air hose and see if it affects the idle, if the idle stabilizes then I'd pull it out and clean it with carb cleaner and make sure the valve moves in it's bore...