There's a guy with an (ugly) track day three-wheeler in Southern California that's supposed to be very quick. I don't know which sanctioning body allows him, but Kurt Belinski speaks well of his setup.
Bottom line is that a three-wheeler can kick ass, but there have been so many E36 M3ty one's made that there's a lot of resistance to be overcome. It's kind of like coming to a formal party in torn and stained clothing. You have to overcome the fact that at first glance everyone thinks very poorly of you.

