D-Jet Problems, Stalls when hot, misses at med. rpms Options

[john_g]

I'm having problems that I'm pretty sure come from somewhere in the D-jet system. I have a '74 914, bored to 2056. Here are my symptoms:

It idles okay. It's a bit rough when cold, but it doesn't cut out on me and warms up to a steady idle quickly (1200 when cool, 800-900 when warm), but when it's been run for a longer time and is good and hot, the idle drops well below 800 and it stalls. It'll start back up right away but only if I treat it as if it's flooded - I have to put the accelerator to the floor as I restart it. Secondly, at mid rpm's, between 2200 and 2800, it hesitates, sputters, misses, and occasionally backfires - this happens whether it's cold or warm.

What I've done or have had done:
usual tuning routine
replaced the CHT sensor
replaced the MPS
replaced the distributor
cleaned the PVC valve
checked for vacuum leaks
checked the TPS, it seems good

Two air-cooled mechanics with good reputations have worked on it and haven't been able to solve the problem fully. All the above helped a bit, but the situation is still there. There has to be some sensor that isn't reading the situation correctly. Any ideas, or ... has anyone had a similar problem? (IMG:style_emoticons/default/confused24.gif)