Small Engines (Lawn Mowers, etc.): fh430v carb issues or spark issues?, air screw, blade tip

Question
I have a fh430v 15hp Kawasaki KAI. I have put new NGK plugs and gapped at .030 per information found online. The carb seems to load up after I put a load on it and I have to back the throttle off to keep it from blowing out black smoke.  This causes me to lose rpms and blade tip speed which is no good.  I have taken the carb off and used carb cleaner to blow through all passages and made sure float was not sticking.  I set the air screw off 1550 idel roughly and turned out till it affected the engine and turn it back to prime setting which was 3 out from seat.  I then turned out 1/4 turn and set black piece back onto air screw which allows me to turn down to 3 or up to 3 1/2.  It seems to want to foul plugs and will drop a cylinder then pick it back up.  If I turn the airscrew out more it does not seem to help the issue at all.  If I take the load off the motor the rpms come back up.  Any help would be great!  Thanks and god bless.
Brandon

Answer
How does it run when you take the air filter out?Could be choking it out if it is clogged up?How is the oil level?You may have internal issues such as a sticking valve or bad rings?I would check that all the little things are right before anything else.If you have not tried taking the filter out and running it I would definitely give that a try.Best of luck,
Jason