Are the rotas bored to factory specs, if not....What hub centric rings is everyone using with their 16x7 rotas, more specifically the gt3???

 

They are not hubcentric. You'll need hub ring, if you're really that concerned. Just go to discount tire and they'll fit you up.

 

what is hubcentric and what is a hub ring for

 

If you'll are really interested.
https://honda-tech.com/zerothread?id=283684
Its been debated many times as to whether or not rings are need. Your lugs will place the wheel on centered. The hub rings just help get them center and center up the wheel bore with the center bore of the hub. Some say that fiction and the lugs hold the wheel to the hub.