Seeing as I have only just read this how about throwing in a few curveballs, misfiring at higher revs, are we talking all the gears or just the top gears, if all the gears is it always at the same rpm or does it vary. Trust me this is very important info.
Also the problem mentioned with the needle and seat sounds more like the slide needle and needle valve, Suzuki tend to use mainly Mikuni carburettors and they have been known to give problems in that area, but it tends to screw up the fuelling in the 1/3 to 2/3 rpm range, a needle and seat that is worn would more than likely create problems in the idle to 1/3 area.
OK I have created enough confusion for now.
