Save your money, the Ecotek doesnt make you car faster, or does it save on petrol, emmisions maybe. Ive had one for about 6 months now on my 172 and I havent noticed any performance gain. It does however make an annoying farting noise everytime you let your foot off the gas, and youll find that engine braking/decelaration is not as respondsive, this is espically noticable at slow speed. ie when the Ecotek is working.
It does look the part though!
But mine is now turned off..