Well, I guess the title says it all.

99E300, 156K on her .. and the fuel economy is almost always 25 mpg, all highway. My assuption was she'd get at least low 30's highway.
Yes, the car is new to me (though I had an 83 300SD and am my second TDI).
Starts well - regardless of temperature, the power is always on tap. The MAF was replaced - had a CEL for it, a few other odds and ends (air filter, etc. Basic maintenance stuff) A lot of smoke during strong accelleration. My first thought is she's dumping excess fuel into the cylinders, but how?
Where shall I look first?