I just took a run with the triangulated strut brace off my 2010 and the only diff I can discern is theres a little more "self-centering" effect--if you let go of the wheel briefly-- from the steering as you come out of a corner than before. I don't even know if the engine cover can be in place as is now but I threw mine in the garage weeks ago so it doesn't matter.

 

They really don't do much and it's a waste of money for the street.

 

They do, just not for this car. They do a lot for a car with a McPherson strut suspension. The RX8 has unequal A arms and there is more structure built into the car.

 

there are people who track their 8 without them.