It's the Throttle Position Sensor, it tells your computer how much gas the truck needs based on how much throttle you give.

Also I'm guessing it's an EFI F150 right? Or is it carbed?

If it's carbed, then it could mean the carb needs to be rebuilt, or a faulty fuel pump.

There is a slight chance it could be because you have low fuel pressure, so I would check that before looking into the TPS.

Umm, as far as fixing it, I don't think you can, you just have to replace it.

Check out this link, it's about the symptoms we have, it's from FTE members.
https://www.ford-trucks.com/forums/1...-cruising.html