I have a 93 5.0 150 It was running fine I parked it and shut it off then I came back out a couple minutes later cranked it up and it shot up 2500-3000 rpm’s started to smoke near the exhaust headers and some out of the exhaust pipes it seemed to be a little wet above the header And the only way to get the rpm’s down was to put in drive or reverse and then it would drop down to 1500-1600 rpm’s but once you took it back out of gear it’s would shoot right back up

 

With the engine off, manually rotate the lever with the green dot clockwise. See if it springs back on its own.
If it doesn't move freely, disconnect the throttle cable and try rotating it.
You probably have a throttle spring issue, or a throttle cable issue.
The two vertical throttle springs should look slightly bulged out, because they have tension on them, that returns the throttle plates to the closed position.

 

Suggest checking the operation of the IAC solenoid on the throttle body. There may be carbon buildup on its pintle affecting its operation. Won't hurt to pull out the solenoid, clean the pintle and the bore which it resides in on the throttle body of any accumulated carbon deposits. Vacuum leaks associated with the brake booster and PCV valve can make the idle speed very high..