Short answer is there is no short answer. Power gains vary. It all depends on your combo and your tuning. A car built and tuned running 116 may not gain much while a car with the supporting mods but on street gas may end up near the same power levels as race gas. Difference is instead of burning the expensive 116 while sitting at the stop light and putt-putting around or having to dial your tune back to run 93 when you're not at the track is with alky you can leave the car set on kill all the time and it only kicks in when you need it. If it is a track only car then the benefit of alky is questionable but if it is a street car then imo one of the best bang for the bucks you can get.