W124, MPG Products to Increase Mileage

My 87 300D has a cruise control with a mind of it's own. Sometimes it works, most of the time just intermittently. I am wondering if anyone knows of a kit to fix, and including instructions for swapping out?

Thanks so much,
Roger

Please help me. I have a 1991 MB 300D 2.5L Turbo Diesel. When I attempt to start the car, it has trouble staying in idle. I have to pump the gas pedal 4-5 times in oder to get the engine to run and have the gas pedal down at least half way to keep the engine running. As the engine runs, there is a cloud of white smoke coming from the exhaust. There is no blow-by, however when I uncap the radiator cap, a froth of bubbles rise after 5 minutes or so of running.