As for the plenum, I want to duplicate the the stock e36m3 set. I had wanted to reposition the alternator so that I can install an oil cooler, but that is a project in its self. I will be making the plenum from carbon composite and use the stock trumpets. The length of the runner through the trumpets and through the throttle body is about 12 inches, which is long but this is the correct leght acording to the pipemax software I am using to design the header and the old Hayabusa set up lenght.
By using the stock stuff it will look clean and be more reliable. The added benifit with moving the alternator to the location of the old A/C compressor is a lower CG, HA HA.