I've used a valve before but didn't really like it too much. Seemed to me that it caused the eng to run rich at idle and hard to get consistant low speed settings. It would be OK at first (the way you tuned it) but as the pressure dropped after idling a bit (and it always does) the mixture would shift. Ended up doing away with it and was happier. But give it a try, maybe you'll like it.

BTW - valve was on the plane when I bought it, wasn't my idea.