[Momaru]

If it was working before he messed with the carbs and that's all he messed with...

There's a very fair chance I'm wrong but: high-end issues may be a main jet or needle, stability @ idle being off sounds like a carb synch issue. It's worth noting these bikes come with 2 different needles from the factory and the mix screws set asymmetrically. Depending on how thorough/careful a carb cleaning he did, it's possible he switched needles on accident. If that's not it, I'd just go thru the whole carb troubleshooting/tuning sequence. There's almost certainly more but here's some to get ya started:

Are the runners securely attached from the airbox and to the engine?
Check the fuel/vacuum hoses for same
Check cable play & attachment
main jets - are they clear & snugly attached?
needle - right needle in the right carb? are they seated properly?
diaphragms - were they re-seated completely? is one torn?
mixture screws - were they messed with?
carb synch - how far off is it?
idle speed - what rpm is it idling?

Could probably check the float bowls too, but I haven't messed with it myself so can't help ya there.