FCABs would definitely cause squirm under braking, but assumed it was alignment settings because I recall you just replaced those poly bushings not too long ago. Full metal bushings is no fun, maybe these are good compromise (paired with blue option):
http://www.rogueengineering.com/Rogu...E46_p_100.html
Honestly you may as well get 11’s for the rear since at very least you’ll want a balanced setup or perhaps even shift more bite to the rear. And it won’t be a total waste because those 11’s you have now won’t last nearly as long as the 08’s so you can keep the 08’s as a backup at the track.
To your point, if you’re not getting heat in those tires then I can see how the brakes are overpowering the tires. Hope you get this figured out though, solving for brake issues is the worst. Plus I think this is potentially one of the best oe brake upgrades for non-M owners.