I was so happy it ran good I forgot to tach it but it was not moving on the ground and it was set lower than my G 62 with electronic ignition runs at (sounds slower) Once I get the card set I will tach it. Hay if the plate works just go fly. I did not advance the trim on the TX to up the RPM in flight. I had good breaking when I went to idle in the air. Sounded very very slow. I would guess the box is helping that low RPM. ROCK solid. I removed the tube to the box (on the ground) and the engine ran the same when the cowl was off. I was at a higher idle at the time so I did not test it for how low I could go. I just put the cowl on and started again. Very smooth motor at idle.

I have been reading the Walbro Service manual from "srm99", this is a must read guys.

So far the only thing I get out of it is that the carb is very sensitive to the inernal adjustments and if I read it correctly also the diaphragm. There may be a spring tension that will work in your cowl set up but I see no way to get a good running engine with out alot of different springs and flying to check it out. Everyones plane would be different depending on cowl cutouts. I do have a older plane I can test this on.

Side note: I used contest grade balsa 1/16 inch. I did not seal the balsa. I am at 550 feet above sea level I would think the balsa will act like a filter and will slowley adjust to changes.