just to answer some of your questions:
-yes it's a diesel
-stock output is 204hp and 400Nm
-stock 0-60 is around 6.7seconds according to most german mags
-there are several different companies that now have software available for this car. the power figures go anywhere from 240-270hp. With 450-520Nm Torque.
-I get around 7.5L per 100Km's
The only thing I miss is the sound of an inline six, other than that, this car is a lot of fun... especially on the autobahn
The inside is still stock, but it has the full M-Package with the upgraded stereo, automatic climate control and a bunch of other little things that all cost extra in germany...