Got a little problem with my '88 4.9L. If I come to a stop without keeping a foot on the gas sometimes the engine dies. If I'm driving down the highway at speed the truck will start to buck like I just killed the engine, but it doesn't die. Then, the fuel kicks back in and it goes. It runs great right up until it doesn't. Whatcha think? Fuel pump. Injectors

 

Are you sure its fuel and not ignition? Usually if its fuel the engine will lay down, bucking is usually ignition.

 

TPS. Watch your CEL and see if it comes on when the truck bucks. If it does it is the TPS.