apologize for not being clearer with my response...W.R., in simple terms, controls the flow to the tuned pipe. One way you can find out if its functioning properly, is when you increase speed/rpm, it will divert water to the muffler, thus having less water going toward the pipe. If you ever experience a 6000rpm max at WOT, this unit(water regulator) is where to start and look at for the problem.