Stalling on deceleration

I got my '00 WR400 to idle and accelerate fine with little or no bog but after it is warmed up it will stall on deceleration after a short blast (20-30 yards) of WOT. The plug reads lean after it stalls. If I can manage to keep it running it pops and does not idle. To restart after a stall it needs to be choked. It will run fine if I ride it mildly or chug it around. I recently added a 10 oz. flywheel weight and did the BK mod. Any Ideas?

Pilot 45, main 165, stock needle in 3rd pos., fuel screw 2 1/4 turns, WB pipe and air box lid removed.

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