That's pretty crappy mileage. Any chance your choke/enrichment linkage is not adjusted correctly? As connie_rider suggested, float bowl height is critical. It's actually pretty easy to verify float level with the carbs on the bike. And while you're there, you can verify whether or not you have overflow tubes by blowing into a hose connected to your bowl drains.
Have you checked your air filter? Could be disintegrating or grossly over-oiled.
Are you guesstimating your mileage by the gas gauge or calculating it at a fill-up?
Does the missing/surging happen under unique circumstances (crosswinds, low/high temps, only after the engine is well heat soaked)? Just wondering why the dealer can't duplicate it.