I've heard that 77 300D is not a strong car to begin with, but mine actually slows down and barely makes it up the standard Washington state hills. At the bottom of a hill I could be going 40mph, and by the time I get to the top it slows down to as slow as 25mph!! So far I replaced both fuel filters, air filter, checked compression, compression is right about 330 PSI in all 5 cylinders, which as I understand is pretty good for this engine (or is it?). What else should I check or do to fix this? Any help or ideas would be appreciated. Roman