Forget the plates. On a tunnel ram, with a lot of nitrous, I think plates are an extraordinarily BAD idea. You need 3 guns, put three port kits on it.

As you know, the more nitrous you spray, the more air you displace in the intake and actual air flow goes down.

My suggestion would be go EFI as well. I am working on a new 3 stage dry nozzle that makes the plumbing very clean for something with 3 guns in a single nozzle