Doesn't the PowerFC's knock sensor just provide a warning light? -Or- can you use your car's existing knock sensor as an input to the PowerFC, which can then make necessary output adjustments to stop your engine from knocking?
If it's the former, then I guess I'll be swaying towards a Wolf3D, as a PowerFC for the RB20DET is a little too expensive, especially when you take into consideration a boost controller.