My question is, would a one way pressure valve or check valve between the tank and muffler help supply a constant pressure of fuel to the engine?
No, it would just make the idle run lean after adjusting and running at idle for a lenght of time. It would trap the muffler pressure in the tank when the engine drops to idle, making it run rich, then you adjust the idle mixture to compensate. Now it idles great, but when you taxi you model out it leans out and quits because the tank pressure slowly drops.