We installed a completely new shower a couple years ago and the water pressure was always fine. Over the last couple of months we started noticing a dramatic decrease in water pressure whenever we set the faucet to the right temperature. We could get good pressure by turning up the hot water more, but of course it's way too hot. Whenever we put it at just the right temp, you can hear pipes rattling and the shower head starts to vibrate. We replaced the old shower head, but that didn't help. Any suggestions?

Give more info on type of shower body. Manufacturer, model and number of controls.

Chuck