The engine light is on. When I am at a stop and start to go, the truck is very is very slow to accelerate and get up to speed. When I put it into Park and press the gas pedal to the floor, the RPM gauge will not go above 3800
The light turned on because the Engine Computer detected a problem, set a diagnostic fault code, and turned the light on to tell you. The place to start is by having the fault code read. Many auto parts stores will do that for you for free.