Something I ran into a while back was a vacuum leak in the air intake hose. A crack developed in the flexible part, and it was sucking air between the AFM and the intake plenum causing it to idle great and run at low RPM but stumble, then stall when you throttle up.
Just something simple to look at.

Tony


80 Toy - disassembled for refitting. '78 CJ-5 still alive. 74 GMC 1-ton full time 4X4,454, B&M TH350,Detroit lockers.