I am not familiar with the MAF kit specifically. It sounds like a more granular method of controlling water flow. A water injection kit will not increase HP or torque in itself, but allows you to run a little more agressive timing or additional boost, either of which will result in a net power gain. At the recommended methanol to water ratio, you would not gain any noticeable power from the extra fuel (methanol), nor should it affect your fuel/air ratio. One option I'd recommend is the Safe Injection module, which can cut off your boost controller if you run out of water.
