If the EGR is functional, the intake manifold is likely full of muck if the turbo is spraying oil. It's entirely possible that the valves are caked with a thick tar-like goop that could be preventing valves from fully closing/seating causing enough compression loss that it runs like crap until it's hot enough to overcome it. Just a theory.

If you want to see if the turbo is your culprit, pull the crossover pipe and pull the breather hose off. Let the engine warm up, then give it a couple good hard revs and see if you get an oil mist blowing up out of the turbo. If you do, you've likely found your oil consumer.

__________________
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]