RE: check valve on pressure line?
I read an article in RCM about using check valves that way. It explained it this way... The tank will only pressurize to the maximum pressure found in the muffler(usually about 5 PSI). Without the valve the pressure fluctuates widely (from 0-5 PSI but only able to maintain about 2.5 through the entire cycle.)
From my experience I would prefer a constant 4-5 PSI than a transient 0-5 PSI. If the throttle in decreased momentarialy the pressure will maintain but if the throttle is lowered for more time the pressure will reduce to the muffler pressure level.
As with any change in supply pressure you will have to adjust the idle and high speed needles. It works fine with engines with draw problems.