[undy]

I'll field #2 and 3 for ya...

I have the 4 bolts on mine. 8 bolts would be better. The more bolts (within reason) you have holding a flange together the better your chances of keeping a good seal and not blowing out gaskets or RTV.

Introducing all 4 primaries in an open chamber, aside from and before the collector, can cause undue exhaust turbulence and possible reversion. That can cost you a few ponies. I think I'd try to find a way to weld a bung on the inside of the collector, in a fashion that would hide the O2/wiring from view as much as possible.

on a side note: I agree with Eric,a minimum of 3/8" on the flange. Mine's 1/4" or 5/16" and is prone to deformation after nut/bolt torque.