Every faucet and shower have a water saving restricter in them. Remove them from the shower head and end of the faucets.
They are about the size of a dime and with about 1/8" hole in them in which water flows out. So the flow is getting restricted from 1/2' flow to this giving you a water saving about a 1.5 gpm.
Below is some more information for the web site please check it out for further help.
Poor water pressure just at certain plumbing fixtures?
poor cold water pressure, hot water pressure, or both hot and cold water pressure or flow that is observed just at some plumbing fixtures in a building while flow and quantity are good at others suggests that the water flow or pressure problems are local to certain runs of supply piping or to the specific fixtures. Check the following first:
- Clogged aerator or strainer on sink faucets - clogging by dirt, debris, corrosion, can significantly reduce both hot and cold water flow at a sink where the strainer needs cleaning or replacement. Unscrew the strainer from the faucet and turn on the water - if the fixture pressure or flow is much better you've probably found the problem.
Look at the aerator/strainer: inspect it, clean it, perhaps soaking it overnight in vinegar to remove corrosion and mineral build-up, or just install a new aerator/strainer.