first off, it doesnt matter if you have the air screw at 1/2 turn out or 2 turns out, if thats where it runs good so be it, theres no performance advantage to having the screw in almost all the way, as I said before you need MORE gas in a piston port engine to rev smoothly then a case reed sled. What you may need is a slide with more cut away to tune in the idle. It is a general rule of thumb that once you get past 2 1/2 turns out on the air screw youd need the next size down in a pilot jet, but you may be just fine at 2 1/2 turns out with 50's once you have run the sled and cleaned out the case and pipes good. You can only do so much tuning on a jackstand!
Your going to always see a fuel spitback spray coming from the carbs on a piston port engine as well, no way around it! On the old sleds like rupps and stuff, your clothes would be absolutely soaked with fuel from the carb spitback coming out of the carb, this is perfectly normal on a piston port engine.
This is what I would do as my next step, reset the float level to std setting, I would then wait until the weather is cold out, below 25 degrees and test ride the sled with the floats set, 50 pilots, 3rd clip on needle, and your 290 mains, run the sled for a little stretch cleaning out the case and pipes and then do short burst of 150-200ft from a dead stop, pay attention to how smoothly it revs or any stumbling problems, check your plugs,piston tops.
then do short burst of 300-400ft and never use more then half throttle, do the same plug/piston checks.
then finally do full throttle runs of 500-600ft, and check the plug/piston wash.
you will be able to isolate the rich settings from the lean this way and tune the entire fuel curve in by doing it in steps.
