TE 250 2009 Intermittent Stall

I am getting an intermittent stall on my TE250. Changing down the gears, if I pull in the clutch to drop a couple of gears for a junction, sometime the engine just dies off. Sometimes fine. Running smoothly, restarts immediately. Often, I just bump it back by letting out the clutch, then it's fine when I pull it back in again. Never seems to repeat immediately. Starts on the button, idles fine. I've upped the idle a bit to see if that makes a difference, no noticeable change. Bike is fitted with PU, set up with iBeat and runs nicely on the dyno with a smooth power curve. Any ideas?

Your injector might need to be cleaned. I try switching over to an iridium spark plug also.