My 94 has started a miss at idle. When i start the truck in the morning is runs perfectly normal. Once i take it on a 30 mile trip and stop the truck and leave it at an idle it has a small miss and shakes slightly. The miss is only at idle and the truck peforms excellent when driving it normal or hard.The truck has to be warm to get it to act up. Could it possibly be a lift pump issue or an injector issue? Thanks for any information to helping me solve this issue