I wonder what Mannhart or AC Schnitzer does for car's with DP's. When we toured Mannhart they showed us a "normal looking" N54 cat/DP... but inside was nothing. They said it was designed for their "Swiss" customers who have very strict Polizei enforcement, as long as it looks stock... it is! But inside was nothing. I think he said they also offer that for the N55. ?
Btw... they were also building a 135i with a N55 head but with twin turbos. That car should be ready in time for the IAA in Sept.