My SDL was starting just like yours - BIG white smoke and lopey/shaky/crappy idle for 5-10 seconds then suddenly "smoothed out". Was delivery valve seals. Been starting on the first or second compression hit with 0 smoke (other than the oil it burns) since I redid them.

You're right though, the early 603's are NOT slow! I've had people in my SDL that were surprised to find out it's a diesel! Certainly doesn't drive like one.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]