Hestitation and smoke: Need advice
 

I have a 1995 300E Diesel. There's 180k miles on it. Power is good but when starting in the morning, it hesitates and then smooths out. Also I noticed when on a long drive, it does good at speeds even around 70 or 80, but afterward shows some white smoke. It also smokes between acceleration temporarily. Even with the smoke, it's not showing any water or oil loss. Any suggestions of what the problem might be?
Thanks - Elizabeth