Unless these things are not maintained or someone has changed out fittings they should be fine.
Check your bellow to make sure it is sealed both on top and bottom and there are no leaks or cracks in the rubber.
The brass fitting on the muffler that the reg screws onto is a calibrated fitting, it should be 3mm ID.If someone changed it to a bigger one that would flood your muffler.
If the spring is the wrong one that will also affect the water flow, I have bought a ski that someone put a rave spring in and that is to weak for the reg valve.
How it works;
At idle or low rpm's there is not enough water pressure to compress the spring and most of the water will go out the top hole of the reg to the tuned pipe. As rpm's go up and water pressure builds it will compress the spring and the bolt on the bottom starts to slide up closing against the stainless washer and diverting more water to the muffler and less to the tuned pipe.
At WOT the reg valve will let out .4 gallons per minute, (I am assuming it is a U.S. gallon)