Curing buffeting is an incremental thing. All too often people buy different mirrors, spacers, windscreens etc and put them all on at once. Sometimes with better end result other time marginal or only minor changes.
Even though it may take a little longer if you do corrective measures in steps you can get a better end result and sometime spend less money by not buying things you don't need like the OP experienced.
Do the cheap things 1st and after each one go for a ride and make note of any improvement. I don't mean a 5 miles shakedown i mean go ride the bike for an afternoon or a couple days.
Bar risers/Bar backs
Then if needed move to the more expensive items like windshield deflectors or new windshields.