Well, I live about 250 meters above sea level, and my Mikarb 28mm needed a 27.5 pilot and a P2 needle jet, and a 127.5 main jet.
The bike comes stock with a 110 main jet, and a 25 pilot jet, and an O8 needle jet. The 25 pilot is sometimes okay for higher elevations, but the needle jet and the main jet are too lean for your elevation. They jet it this way because it comes from the factory all plugged-up at both ends, and also needs to pass emissions testing, so they don't put any fuel into it.
If you have a decent air filter and have dumped the crappy stock bazooka muffler, you need richer jets.
"Hunting", which is a term for an unstable idle speed which cannot seem to settle down, is a symptom of lean mixture. If you can close down the air bleed screw, and the engine doesn't die, then it's too lean in the pilot jet. This comes right from the Mikuni tuning book.
Not too sure what kind of dealer you have in Auckland, but it sounds to me like he isn't too knowledgeable.