I have this same engine.........and without going out to the garage and checking(and I dont want to mess with my settings
,I'd say your 4 turns out is still WAY too far out causing your engine to run like crap. Sure it will run great at idle up to maybe 1/2 throttle,but that is only because its still running off its slow jets. Once your throttle get over about half way,your main(needle) jet will take over and that is where your problem is. I'd guess my needle is 2 and a half turns out,but not sure.
Start your motor and get it to where you can open the throttle wide open and turn your needle in until your motor dies. This will mean you've leaned it as far as it can go causing it to starve itself of fuel. Just make sure you've broken your motor in good first and dont take forever to perform this task. After it quits,turn out your needle a bit and go from there. And USE A TACHOMETER to tune your saito if possible....it helps.
Once you get it close do this.......Start your motor,get it warmed up good......let it idle,then slam the throttle wide open and listen to it closely for the next few seconds. If it revs up real high upon opening up the throttle,then slows down a bit after about 3-5 seconds......its running rich,and trying to overload itself with fuel. If it revs up high and stays right there forever.....its either right on or lean. And you'll need that Tachometer to tell if its too lean as it will show you your not getting enough RPM's out of your saito. And this is because your needle is not out far enough to give it enough fuel to run high enough rpms. If you get too lean,it will not only not be good for your motor......it might deadstick alot on you during certain manuevers.
Took me awhile and alot of playing to figure all this out..........but keep it in mind and it may help you. And mine still smokes good. Maybe you have it so rich,your not getting enough heat from the motor to burn the oil good and its just spitting it all out.
Oh.....and I doubt you should have touched that low end adjustment. I've never touched my out of the box and idles good and is the best transferring engine I've ever seen.