With all due respect Simon, cars with much less power than yours claims to be have run the same or faster times at Elvington using OE manifolds!
I don't know if you do or don't know what you're doing as I am not familiar with you or your credentials but i'm not sure a 13.1 time is really a great sales pitch.
The above manifold is a volumetric copy of a Mountune, I ran it on my demo car for some time to develop it. Performance wise it got me a 13.1 quarter at Elvington.
My other manifold which is a based on a Pulsar plenum has recorded 380bhp at 26psi on my ZVH.
So I feel it is a little unfair to sugest that we dont know what we are doing!
Simon.