My X2 idle very high sometime after a couple start and stop sometime high enough if you start in gear it will move .If it very hot outside it will idle so low it just stall and you have to give it some gaz to start it back.the bike is on good shape valve adjust clean the throtle body change plug no vacuum leak .

 

I'd try adjusting the throttle cable first, there should be the maximum of 1/8" play in the throtttle, there is an adjustment just a little ways down the cable towards the handle bars, this should hopefully fix your problem

 

THey had to re-flash several efi machines to get them to idle and run right.

 

I rode a friends 08 X2 efi on the weekend and noticed it idles low and if I let off the throttle and came to a quick stop it would sometimes stall. More often if I had the ADC on. I wonder if this could be his problem, Good to see lots of advice.