Hello! new to the page, and new to the 8th-gen Ford's first time owning one of these body styles and a fuel-injected I6, so please excuse my ignorance lol.

I just purchased A 1987 F150 EFI 300 6. truck was running well, went to start her up today and started down the road, I was lacking power and could barely move in second gear as if the truck was only firing on 2-3 cylinders and not getting fuel, parked the truck and if you slowly ease into the accelerator it sounds and runs fine, but if you give it any gas very suddenly it almost stalls and will not kick back and sounds like only two cylinders are firing, and it's starving for fuel. After a trip to the parts store replaced the plugs, wires, fuel and air filter, checked the fuel pump and it seems to be strong and working well and very little change at all, I did notice the fuel filter was dirty, but after replacing it, it does not seem to have helped much, so I'm lost on what to do next, thanks for any advice!

 

How did you determine that the fuel pump is strong? Did you hook up a pressure gauge? And keep in mind that your truck has multiple fuel pumps, a low pressure(in tank), and a high pressure(frame mounted).