86' F350 302 Hesitation Problem

[yummybagel]

This is a friends of mines truck that he a two local auto shop have been trying to solve for some time now. The truck hestitates after driving for a little while, and the idle is high it is around 1000rpm to 1500rpm. However you can fix the problem temperarily by putting the truck in neutral, and then back into drive. This seems to solve the hesition problem for a breif period, then it returns. A local auto shop said they could fix the high idle by replacing the idle air control valve and the mass air flow meter, and the hesitation could be solved by replacing the distributor. So far this has had no luck solving the problem. He then took the truck to a local ford dealer, at which they diagnosis was to replaced the two gasket associated with the throttle body, fuel delivery module, fuel injector flush and re-flash the pcm. This is were we are at now with this concern. Has anyone seen a truck perform like this before, please help with any input you may have into this situation.
-David

[mustangmike351c]

if its an 86 then it doesnt have a mass airflow. I would say it has a vacuum leak. check it with vacuum gage it should have a steady 15hg.