I am actually doing what you are talking about now and am installing my water meth kit starting this weekend. What I did is used an AEM FIC to intercept the TPS, Rail pressure, Boost and MAF sensors, I have RPM as well. I can control the water meth pump and nozzle solenoid using RPM and boost pressure. I understand your concerns with too much torque in the lower rpms. Itís also my goal to limit the torque down low but get as much power/torque as I can in the upper RPM. Using the AEM, I have been able to fine tune the fuel pressure to push the power as much as I can for all RPM and loads while not getting knocks or any codes. FYI, max rail pressure you can push is 1800bar or 4.5v from the rail sensor. Anything over that and the rail bypass valve returns it to the tank. Great work!!!