It was just a thought, stepdad had an 89? F-150 5 speed, ran like you had never driven a stick. It would hesitate when you gave it gas so you would give it a little more then it would rev way up, you'd let off but it would stay high for a few seconds. Driving on the road when you shifted the rpm would stay high between shifts even though you had let off the gas. Always thought it had to be tps sensor, didn't get a chance to replace it before he got rid of it.