I've had my 93 300D 2.5 turbo about 18 months and always had this question. When I leave work about 3 or 4 minutes out I have to head up an on-ramp that is an upward incline. So I put my foot in it to get up to speed and nothing is noticeable in the daylight. However when I have someone on my tail in the dark the cloud of crap coming out of my tailpipe is pretty impressive! I can hardly see their lights as I run up to ~3200 RPM before it shifts into high. Once up to cruise speed, no more smoke noted. This seems to happen when she is cold and the air temp is cold but I have seen a little smoke on inclines at cruising speed when she is warm. Is this just a diesel thing? I actually get a kick out of it, I hope it isn't a problem. Part of the fun of the car honestly, but I wouldn't want to be the sap behind me !