the shop manager of the performance machine shop I've used for the past 15 years says that on their race car, they don't even use exhaust gaskets -- he says you just make sure the header flange is machined flat, and they dollop some copper anti-seize on the mating surface and cinch it down.

copper is not the same as the aluminum stuff; it's rated for higher temps.

I'd try that.

what is it about the OEM gaskets that don't work? is there some heat shield material riveted on like on the 22R exhaust gaskets? I just had a similar situation with my DT Header. ended up clipping/grinding the rivets and pulling the heat shield piece off, and it worked out okay, so that may be an option for you as well depending on why the OEM gaskets won't work.