Sorry to answer my own post but perhaps it is this ? Seems to match the HP claim, but would appear to be a lot less than $15K. A post on the US forum suggests $4K US which would sound about right for cats and an ECU tune.
Mr Noelle is ex head engineer for 9 years at Alpina, but even so - an extra 60hp odd from cats and an ECU tune ? I've gotta say i'm a bit sceptical.
http://www.noellemotors.de/4_2l_engi...f5d2242.0.html