If youre going to do one or the other, a properly sized intercooler would be most efficient and give you the best gains. Also, unless youre going to run a high powered drag engine a water/alky injection setup really isnt necissary if you have an intercooler. If you plan on running a draw through setup however, water/alky injection is pretty much your only option. both will help, but on nay kind of street driven vehicle, water injection really wont give you the results that an intercooler will...especially at the horsepower ratings that one would expect from a six.
