after some quick searching here:
http://www.sccaforum...rums/aft/392890
NC mazda miatas have "Ice Mode" in their ABS controller. I guess the RX8 does not.
Ice mode is a safety system which cuts off brake assist when it thinks you're driving on ice and one wheel is completely locked up for a really long time. it happens when your lift a wheel during cornering on a track with sticky tires and stiff bars. You can also just pull the ABS fuse and disable it all together when you race then plug it in on the street.
if you want ABS when your racing, then swapping to the RX8 setup could be safer so you don't loose brake assist after a long sweeper.
-Z