I am not sure but is the B18 AI Intake manifold the same size as a P 30? I belive what i'm asking is whether the ls intake mainfold that same size as a B 16 maifold?

I'm pretty sure (almost positive) that the B18a IM has longer runners, to help it produce more torque. However they are not interchangeable.

Yeah, they are not interchangeable. GS-R head, LS head, and B16/ITR heads are all different.