Idle speed issues
The throttle position sensor plays a role in older ford EFI systems, but in the case of yours...it will not, so don't adjust it.
The EEC looks at the position of the TPS at key-on and says "that's closed". In the earlier EECs, the voltage out of the TPS could effect idle quality.
A stuck IAC, incorrect base timing, misadjusted throttle plate, vacuum leak, or rich condition can all cause elevated idle. It is NOT normal.
That said, check your idle speed with a scan tool, not the factory tach. The factory tachs are usually VERY far off.
After that, I'd start looking for air leaks. Any hole between the MAF and the intake ports on the heads...even the size of a pencil lead...can do this.
Is your check engine light on? If so, what's the code?
Next, has anyone messed with base spark? Does this truck still have a TFI Ford distributor?
What do your long term fuel trims look like after 5 minutes at idle on a 160+deg F engine? If you don't have an OBD-II scan tool with datastream, you need one.
Let me know,