LiquidFlux

I picked up a GT Air for 350 at 2014's MCN, coming from a budget helmet I appreciated the better build quality that came with the Shoei but most of the problems you mention I can relate to.

I avoid the dropdown visor nearly all the time except worst sunlight conditions, unless you click the visor into the fully sealed position the whistling does exist, and I've accustomed to pulling the helmet from the chin down so I can ride with a slightly adjar visor. Without the chin down or visor any more open than it can be without quite being shut, and I can't much handle 50mph+ which I could with a previous cheap lid.