Shower lost its power?

My power shower is now just like a normal cheap shower with no ommph. We are disputing if it is the pump or the booster. As it is still working and not making a noise my theory is that its the booster..but I am no plumber..my hubby thinks it is the pump...but I am sure it would be making a noise if pump gone. When the booster used to kick in it used to make a noise...this noise is no more...what do you think?