Watched a throttle replacement the other day on the tube. Sure looked like a "fly by wire" system to me. So there is either a program problem, a feedback loop, or electrical interfearance. Doubt there was anything at all with the actual peadle assembly at all. I'd fix by patching in a seperate wiring harness and linkage and throtle setup, sharing only a ground with the rest of the elecrtical system. And I'd completely disconnect the original wiring attached to the engine maint, system.