Just in the last few months I've noticed the truck idle start to surge drastically when the clutch is pushed in and I come to a stop. Then after 30-45 seconds it quiets down to normal and is very quiet. Also whenever the gas pedal is used the engines kinda jerks when gas is applied or when you let up on the gas. Also since this started happening my gas mileage has gone way down. Probably at around 18-20mpg now in town. Any ideas? I've replaced the wires and plugs(new E-plugs), changed the oil, oil filter and air filter.