Here's one from GReddy Performance Products that should answer the biggest criticism of Mazda's nifty RX8 - not enough power and torque.

This Turbo kit for the RX8 rotary increases horsepower by more than 29 percent, to 261 hp, and bumps the torque figure from a limp-wristed 125 ft/lbs to a beefier 176 ft/lbs, while flattening the power curve to give more mid-range grunt.

more details.