My 1991 E250 351ci

van with EFI intake developed a throttle sticking problem. I took it to my mechanic who replaced the throttle cable & return spring. He also removed the throttle body and removed the gunk on the butterfly lever post that was causing the problem. When I got it back I noticed the idle seemed higher, I took it back and he retarded the timing slightly and said it was fine. It still seemed high to me so I took it to another repair shop who replaced the computer chip that controls the idle, it was still the same, they said there was nothing else they could do.

I attached my Actron tune up analyzer, after starting the engine and letting it warm up the rpm idle in neutral was 850, 750 in gear.

When I rev the engine the idle settles at over 1200 rpm where the dial on my analyzer maxes out, I suspect it's probably more like 1300.

When I turn the engine off and restart, it again idles at 850 in neutral, when I bip the throttle it increases to 1200, EVERY TIME. When I turn the engine off it resets.

Something is happening when I step on the gas and it's not mechanical, it resets when I turn the engine off.\

Any questions or input would be greatly appreciated, Thanks in advance.