Hmm... I'm having a similar problem with my ' 84 760 Turbo. My fuel mileage has dropped down driving to and from school (160 miles each way). It sounds like you might need a new fuel pressure regulator if you're getting fumes from that small vacuum hose. Mine is actually leaking now but I haven't gotten around to replacing it. I also believe that this is making my main fuel pump a little noisey (which is new). I wasn't aware that a 740 had an EGR valve. Maybe someone here can elaborate??

BTW, my turbo doing the same thing as yours (oil pooling in the duct work). I'm going to replace it with one from FCP soon ( around $600 I think). There's also a turbo rebuild shop near my home in Charleston, WV that I'm going to check with. Some people on the board say that a turbo can be redone for ~$300 if it isn't too trashed. I'm also hoping that this will help my MPG and oil consumption (1 quart per 400 miles of M1). Yours doesn't seem to be using nearly as much oil though.

Good luck with it.
Dave