New to Harleys having ridden Japanese for 25 years. Why didn't I do it sooner?

Can anyone tell me if the setting of the idle screw, once having removed the blanking plug, is about 3/4 out from in, this is what it was having drilled it out. Looking at making the factory set 'leaness' a bit richer. I'm running stock pipes, filter and jets, jets are 42 and 165. Can I run on just a K&N filter and up the 42 to 45? Tried setting the idle but it's not running well, currently at 1 1/2 turns out. is this about right? Any answers or pointer would be appreciated, cheers.