I found this interesting 'Ring test over on the German e46 forum. It is quite old, from Oct 7th, 2008.
http://www.e46fanatics.de/test-und-f...sind-drin.html
Post #10.
BMW Performance 135i vs
Porsche Cayman S
What is
most interesting is that the 135i was tested with ALL the Performance goodies, even the PPK (performance power kit!) plus all of the CF stuff.
BMW Performance 135i 'Ring time =
8:39.2
Porsche Cayman S 'Ring time =
8:31.9
Dackel