Idle won't return while driving?

After bike is warmed up and I drive it the idle will not return when changing gears. I have cleaned these carbs and are 99.9% sure they are clean, I have oiled the cable and linkage and it is completely free to move. Other than the suggestions that you may have, I am thinking that I will clean and put back my original jets and take out the ones that came with my rebuild kit from Z1 Ent. I am sure they sent the same size jets but maybe not. I see on threads that this problem is a vacuum leak sometimes, can someone tell me were this leak can occur and how to check for it. Thanks Don

Finding a vacuum leak is relatively easy: get a can of spray carb cleaner,warm up the engine, and spray around the ducting/boots before the carbs and between the carbs and engine. If the idle goes up, you've found your leak.

The correct term for the manifolds the carbs attach to is "Carb Holders", they have a rubber liner that with time and heat can crack letting in unfiltered air that will affect the idle.

The only good repair is to replace them, while you're at it replace the rubber plugs that fit on the vacuum ports for carb sync. as they can crack too.