What are the code numbers your getting?

My F150 was doing the same thing when I got it. What was happening was the TPS voltage was dropping to 0 under hard throttle and it shouldn't have been doing that. I replaced the TPS and also found out the pigtail from the ecu harness had gone bad and it was the primary reason that my TPS failed. I replaced both the TPS and pigtail and haven't had any problems afterwards.

Yes the Throttle Body does have to come off, but a new TB gasket is under $5 so just buy a new one to be safe.