oil out the tailpipe and lots of smoke (white?) would incline me toward a blown seal in the turbo perhaps. At least that's the first place I would look.

Aside from the problems you might have / find I personally think this is one of the Benz cars I would be most inclined to own. I have seen perhaps two in my area for sale in the course of 10 years. I think a manual trans version of the 2.5 would be great.

steve a