A properly set up alcohol injection kit works great. First off it should be set up so it only comes on at WOT and at say 20+lbs of boost. Propane works also but i would rather have a 1 gal cell with alcohol in it under the hood then a propane tank in the car. Just remember no matter how well you tune the car on 93 octain, alcohol will only make it faster. And if set up right you would never use it unless you were in high boost at WOT.