Hi !
I have almost the same setup as you . except my dome are 21 cc and I'm running 91 octane gaz,open air box no lid K&N pod.
right now I use 320 and it's perfect for my elevation (sea level) and my climate 15 to 25 celcius degree (Québec ,Canada).
plugs have the perfect color and no bug when I drive .
I hope that can help you .