A local guy is "downgrading" from a 540hp NA Miata to a 430hp NC Miata. Why? Flyin Miata has put more engineering into the NC V-8 conversion to allow the car to better use the power. While the NA cars cope surprisingly well, the reworked NC chassis is much better.
The 430hp NC will still be blindingly fast - and I bet faster in most circumstances thanks to the ability to use the power and that after about 400hp, the little Miatas just burn it all off in tire smoke anyway...