I bought a 1978 300CD with 250K miles about two months ago. So many problems and I've never worked on a diesel but my income is too modest to afford a mechanic. I'm just a humble computer guy. Okay, enough blathering. Recently, the power assist on the brakes gave out and, simultaneously, the car wouldn't shut off when I removed the ignition key. I have been told that I need to rebuild the vacuum pump. After a week of manual braking (that thing's a beast to stop) and manually choking the engine when I get to my destination it's developed a new problem that is far more devious. My commute to and from work is about thirty minutes on the freeway (one of the reasons I wanted a diesel... for the mileage). After about twenty minutes of cruising at sixty-five the car suddenly starts to feel like it's laboring. No matter how much I mash down on the accelerator I can't get it to go over fifty-five (no, it doesn't have a governor) and it feels like it's struggling. When I try to go up the hill towards my house it shifts into low gear far too early and revs up but barely gets up the hill. I've asked friends, who work on cars as a hobby, and one suggested that it might be the injection pump (or timing pump?). Can anyone confirm that or think of anything else? I really would like to be able to get this beast back to a beauty. Thanks, in advance, for your help.