Firstly,the last guy had it leaned out if he was 2 1/2 turns out.By turning it 2 out you richened it a bit.If your idle dropped when you turned it in to 1 1/2 you've gone too far.For your airscrew setting,you want the highest idle-2 turns by the sound of it.Once there,turn your "idle screw"(above the Keihin marking-likely black plastic head with a spring behind it directly to the rear of the bike from your choke knob)to the left(counterclockwise) until the idle drops to where you want it.The airscrew shouldn't be used to set your idle as this gives you the wrong setting.
If two turns out turns out to be your best setting you're in range but almost at the lean extent.If the temperature where you ride goes up much more in the summer you can go out to about 2 1/2 then but after that you will need to switch to one size smaller(leaner)pilot jet.
As for sound/feel/performance setting,I set it first by rpm/sound then ride it.After that,try turning it in 1/8 turn or so to see if it's a bit better-if not,go out the same and try it again.If both are worse,return to your original setting.Sometimes the best performance will be slightly to one side or the other of the max rpm setting.Of course,once the temp changes you'll have to readjust to maintain it.Colder temps-richer/hotter temps-leaner.
That's why it's good to have the bike jetted for your usual riding temps.That way,slight temp changes can be taken care of quickly with just an airscrew adjustment.Eg.,if say your usual riding temp is 70'F and you have a pilot jet in it that allows you have your screw at 1 1/2 turns out you can typically go about 1 turn out for 60' or 2 turns out for 80'.More or less anyway.