After major repairs the truck will not go over 45 and barely accelerates?

Hi, I have the truck listed above with the 5.4L Triton gas engine. After recent repairs (serpentine belt, tensioner, timing cover, head gasket, and spark plugs), the truck is having issues. It runs and idles fine at first, but after driving for about 15–20 minutes especially around 35–40 MPH or going uphill — it starts to lose power. The wrench light and check engine light come on, and the engine begins to surge or rev without accelerating properly. It won’t go over 40–45 MPH and feels like the transmission is stuck or slipping, with the truck shaking under load. If I pump the brake and tap the gas, it will temporarily respond. Several codes popped up, most of which point to the throttle position sensor, which I’m planning to replace. Could this be a failing electronic throttle body or accelerator pedal sensor, or is there another issue that could be triggering limp mode with these symptoms?