Strange Kohler Shower Body Valve issue

from what i've been told this isn't your normal shower issue

When i turn the either the hot or cold water on in the shower, the same amount of pressure comes out no matter how much i turn the knobs, but works normal in the sink. I am also getting very little pressure in my shower which, but am getting normal pressure in my sink which is split from the same line.

I have replaced the valve stems in the bathroom already, and that didn't fix the issue. I'm thinking it would be the shower body, but how could it be the shower body when it's nothing more than a passage way for the water to go?

Are you sure the knobs are hot and cold? On some of them, one is volume and the other is temperature.

i'm 100% sure of that

bedies the fact that you can tell when you turn the knobs, i have opened the wall from behind, and can see the supply lines


also it's 3 knobs

hot, diverter, and cold

flow on showe valve

Have you checked the inlet filters to the valve (normally located on the left and right hand side of where the thermostat handle?)

Filters?

That answer probably doesn't even apply to this faucet. It has no filters, nor does it have a thermostat handle.

valve

If it has a diverter, it must also be a tub, and not just a shower. How is the flow to the tub?