1988 ford f-150 idle problem

my truck has a very strange idle i can not figure out y i have try almost everything when i start it if i push the gas alttl it will idle up and own alot and just act retarted any suggestions

have you tried the Throttle Positioning sensor ----

I did have a truck one time that the idle went real high, it was the power brake booster went bad, and the lack of vacuum made it idle high, the mechanic took the vac line off to the booster and pluged it off, and the idle went right back to where it should have been ---------

that seems to make sense because i have no brakes half the time its almost like the truck is not running