I recently replaced the fill valve in our toilet with a fluidmaster. The toilet is flushing fine and fill valve is working as it should, but I have noticed I am now getting a gurgling/turbulance like noise coming from the overflow tube in the tank after a flush(did not get this with previous fill valve). I have tried to figure out what is causing the problem with no luck. It does not make the noise until the flapper is completely closed. I have the refill tube position correctly over the top of the overflow tube, so I know thats not the cause. It seems I can only stop the noise if I restrict the flow of the water from the refill tube to a trickle. Any ideas on what might cause this?