E46 M3 2002 is either Siemens MSS52 or MSS54. Both can be read with Galetto tool. I've not come across a diesel M3 yet. :-/
If you are going to do any modifications, be very careful what you read on the internet as there is quite a lot of misinformation.
There is also lots of good information. Much of it from decompiling the ECU data, a little from actual testing.