After cursing my Raptor from one end to the other, I think I may have it right. I was running 165, 170 and 27.5 pilots with the BG full exhaust and a Pro Design filter kit. It ran ok, but it still didnt feel right. So as a last resort I made a run without the filter lid. Man, did this ever help. Now it pulls like I wanted it to all along, no more sputters, no more falling off on the big end, just solid pull from bottom to top. The reason i never tried this is because the guy at Pro Design stressed for me to NOT run without the filter lid. Oh well, live and learn.
oh yeah, what are you guys doing with the crankcase vent tube that runs to the airbox lid.

 

I used a differential vent off a GM truck. It fit the hose perfectly. You can pick them up at any GM dealer for a couple of bucks. It fit the hose perfectly.

 

I have pics of what I did to my box on my site, click on raptor airbox

http://www.geocities.com/raptorterry

there is a pic of the breather tub also