this guy says they add downforce?

http://www.bimmerforums.com/forum/sh...threadid=72311
" On these cars the Exhaust Systems are bolted to the cars and not suspended by rubber hangers. High Reving engines cause a lot of exhaust pressure to leave the tips. By Turning the tips upwards, the exhaust pressure as it hits the atmosphere is now pushing down on the exhaust system causing an added amount of Rear Downforce applied to the rear of the vehicle, Thus increasing the performance of the Car "