Inside that $130 box there is nothing but a few resistors. This is the same weak solution as the "Boosterplug".
This isn't the best way to adjust tuning of a bike. You will get strange swings in air/fuel ratio. It almost feels like going back to carburetors that are hard to tune. Sure you can get it to run a little richer here or there, but your air/fuel ratio isn't going to be that perfect straight line that that you would get with a Power Commander and a trip to the dyno.
The bottom line: you get what you pay for. (or in this case, less - a box of crap for $130) I wouldn't put one of those on my bike. Save your money and do it right, at least if you intend to keep your bike for a while.
I sent a request to Dynojet to confirm that the G310R PC V unit would work on the G310GS. I'll let you guys know what they say. I don't see why it wouldn't.