First, of all your problem is not with AFR but with air leakage. No matter how much improperly the AFR is tuned, then also your rpm will not shoot by more than 500 rpm. My bike idles at 1000 rpm when cold and 1200 when hot.
There are three possible causes of your problem. They are:-
1. Air leakage from around the carburettor. Check connection between carburettor and head.
2. Tight tappets. Was your tappets adjusted, then a tight tappets can cause this problem.
3. Battery problem. If your battery is undercharged then also you will get the same problem.
Regarding carb tuning i am posting again and all members in this thread please note the same:-
1. Pull out the air pipe between the carb and the head. You will see that a rubber pipe is fitted to carb insulator. Pull it out.There will be a brass pipe. Close it with your finger. If you do not close it your bike will not idle.
2. Now set the mixture screw to 1.5 turns out.
3. Now start the bike. Be sure to close the air injection at carb insulator with thumb of your left hand.
4. Now increase the idle by idle screw to 2000 rpm.
5. Now slowly turn out the screw. I repeat very slowly.
6. You will see the idling rising. continue until maximum idling is obtained. Beyond a point idle will not increase at all and instead decrease. At the point where idle is highest stop turning the screw.
7. You will see your idling is highest and also the rpm needle is constant.
8. Now decrease the idle to 1.2k. stop the engine.
9. Now remove your finger from carb insulator and connect the air injection pipe.
10. restart engine and check idle.
WHY TO REMOVE AIR INJECTION AND CLOSE THE PIPE?
The air injection in extreme works on pulse and injects part of exhaust gas into inlet to control NOX emission. But this dilutes the mixture and thus proper tuning is not obtained. SO remove it from carb insulator just after carb and before head. After removing close the hole as your bike will suck air and not idle. Also in this type of carb if you do not remove the air injection pipe then your idle will not decrease after some turns of screw out. If you remove the pipe, you will see that after idle increases to highest if you turn screw out then idle will decrease. If the air injection is connected then idle will not decrease no matter how much you open the mixture screw.
How to know mixture is set correct?
When you turn the mixture screw out, you will see the idle will increase. At one point idle will be highest. But there is a catch. Check how the idle is highest. At one point the idle will be highest but bike will be smooth. At slight another point, idle will be highest and bike will vibrate. The point at which idle is highest and bike vibrates, that is the correct setting.

Carb tuning is not easy. You must have read that there is no substitute for experience. This applies to carb tuning. Ask SHOEB, he was also not able to get correct tuning. It was until he asked me several times and i explained him each and every detail in minutest possible way. There is no fixed turn which works for all bikes. You have to find your bikes work at which setting. So follow the above steps.

Factory tuned doesn't means perfect tuned. My mechanic tunes bikes and even company cannot tune like that. Yesterday i tuned my extreme from my mechanic and believe me it has become so smooth that you will feel like unicorn. Before this it was in factory tune. Yesterday first time my mechanic tuned and my bike feels much better than new.