Needle valve.... I found a solution. The typical OS FSR type needles are identical length and thread (and sealing) but the taper is over twice as long . Will try today.

Did take some real quick muffler pressure readings yesterday and despite this being a fairly restrictive muffler (from an OS 40FP) the pressures were lower than I suspected. Also I noted that the mixture setting does change the pressure independent of rpm. As you tend toward lean at peak the pressure drops slightly which is not really what we want. The slight pressure drop seems to proceed the rpm decay just slightly..

The other thing ii noticed is that the pressure is a bit more linear that I expected and this bears out with most gas conversions going rich in the mid range - My quick running setup yesterday pushed very little pressure under half throttle when transitioning (and running) through the mid range. Muffler pressure is typically higher here...

We could drift down the road of adding sensors to measure and relay data but in an effort to KIS I think we might have two basic options now - the E-pressure is not much simpler than the solenoid setup but it is cheaper as the pump is $3 and easy to find.

Will do some more runs today and get some better data if I can...