Sometimes my truck I recently purchased will "spit & sputter" for a while. It happens once the engine is fully hot, will be cruising along and feel the miss and can see the tach fluctuate. It will be bad enough to make the whole truck shake and you'll think it will break down, but release the gas pedal and coast just a short distance and it will then run normal, wont do it again unless it gets cool. Appears to have new plug wires, any ideas on what else to replace? I have a new air filter and cleaned the throttle body and it does not have a replaceable fuel filter. It is a 98 4x4 with 5.2 engine. 148k miles.