After turboing 3 mx-5's, i wouldn't bother doing anything with the motor except a turbo, the first b6 na went from 58rwkw to 165 with no internal mods, and was thrashed daily for 6 months till it was written off, and the b8's respond even better. How do you find the chassis stiffness, the last one i did we fitted a full butterfly brace, and it seemed stiff as.