91 F150 6cyl is still missing. Replaced the plug wires and had the throttle body gasket replaced. Dealer tells me to replace the entire throttle body. Does anyone else have a suggestion for me? It's like there's a hesitation at certain speeds, used to be only at about 40mph, now it's from 20-70.

 

I've been having the same problem - try the Bosch Platinum+ 2 plugs....its fixed my missfire problems in the past....

Robbie

 

How long since you changed the fuel filter? Might be a fuel problem just based on speed ranges it occurs in. Also check fuel pressure. Good luck finding the problem.