I spent a day at AVA, a local tuning company, which was arranged through the college course I was attending. They did not rate these power enhancing boxes. Allegedly......(here we go again!

) they retard the ignition to begin with, and then after a certain rev limit, it advances the ignition, so what you feal is a surge in power, but it is only surging up to what it would be as standard. It infact give you less power at a lower rev band. Allegedly. You could get a re-programable chip, and have someone clever re-map you engine while you drive via a lap-top. My mate is going down this road with his race car once he gets throttle-bodies fitted.