Hey Turbotexas!!!
Don't I know you from somewhere?LOL (Buggy news)
Glad to hear you got an oddy!!! You will never go back to the China Karts after taking this step...
I will give you a couple of my cents worth on the air box...
I don't have an oddy, but do have a pilot...I ran several different test with air box mods about a year ago, and here are my results...
The previous owner had the machine jetted so rich that it wouldn't run with the lid on the box, but take it off and it would run decent, but still rich...I dropped my main two sizes, lowered the needle a notch, and it ran better, but still a tad rich, but just couldn't make myself ride around without an air box lid...
I added an extra hose and a homemade air scoop, which is more restrictive than an open lid, and the pilot came to life even more...Better throttle response and overall performance than with the lid off....
I went even farther and made an adjustable air valve like you referred too just to play with air flow, and see what was affected by increaseing or reduceing the amount of air the engine could pull in...
Believe it or not, I found the engine performed at it's best when I reached a point where there was just a bit of restriction in the air box...
My point being pointed toward your question about removing the box....
I have seen several different set ups that run a filter off the carb,and I am sure that it does help in the top end, but IMO, I think it hurts the performance when getting to wide open.....
I believe there is a fine line when dealing with the pressures in the air box, and finding that will give far better performance than just trying to get as much as you can with a filter on the end of the carb...
Kinda like those China Karts...You know how many have tried that mikuni carb application, and most do a filter mod at the same time, by-passing the box...I have yet to hear of anyone that has done that mod and been happy with the performance...They chase the jetting and never seem to catch it...No one that I am aware of tried the new carb with their stock box, and maybe just opening up some small holes and noting the results...IMO, the filter without the box is their main problem...
Sorry for being so long winded...Oh yea, one more thing about the air valve...I can adjust jetting by about two sizes in the entire range by opening and closeing it...They do work....I think I have some pics of it on this sight somewhere...I will look...
Hoodlum