Steve wrote:
Every faucet in my house performs poorly. The first thing in the
morning, they flow pretty well for a few seconds, then slow WAY down.
Some days it's the bathroom sink other days it's the tub; every day it's
the kitchen sink.

SNIP

Focus on searching for a Pressure Reducing Valve.
Might look like this:
http://www.cashacme.com/pressregeb86.html

There is no reason that your pressure gauge
should read 40psi while street pressure is 100psi
unless you have a PRV.

There could be other reasons for the reduced flow,
such as restrictions mentioned, but start with the PRV.


Jim