chug-a lug-a feeling is from too lean. I recently did the Dyno Jet, a Supertrapp, a K&N, Airbox, and slide drill on my 06 DR 650.
So I have tried almost everything with this bike trying to tune it. Basicaly the Supertrapp is loud and is not ideal for the DR650, I think I will maybe get a Can for a GSXR 750 or something and use that instead.......
At anyrate I had the "chug-a lug" going through most of my ordeal. I drilled out my stock Jet to a 165 with the stock needle this was after the Dynojet kit wasnt working on the 4th step, so I gave up on it. That actually worked good with minimal Chug alug.
My current setup:
K&N with top of Airbox open
170 Dynojet needle at 3rd position from bottom
And no more chug a lug, at 160 Dynojet I had major chug alug with this setup. Im going to drill out one of my smaller 150 Dyno Jets to what a 180 would be when I get my new can for my Supertrapp pipe and see how that goes.