@ m3james
Since your m3 has a custom exhaust system and a turbo you can basically forget to get it registered in Germany on your own efforts. The only way is to contact a specialised dealer like
www.uscarscenter.de or
www.uscars24.de. They would probably get the German warrant of fitness, but I guess for a fortune only...
The Porsche idea sounds much better and @ BlackPJ80 the 993 was produced until 1997.