What is a "small dose" ? I use a 7gph nozzle and it has always kept kr to an absolute minimum on 93 octane, 18* advance and a 2.6 pulley.
For the op's setup i would say a 4 or 5gph nozzle would be the most he should run.
BUT if you are running a gen III, i would avoid the meth injection due to the fact that the water/meth will just destroy the ****ty coating on the blower rotors.