440 what am I missing here?

Beat me to it, but I'll go ahead post to back up what PRH and AndyF are saying about the manifolds and reversion: You not only have pumping loss from the piston having to push the exhaust gasses out, but you also have a big single plane intake and 108 degree LSA. Now at low rpm when the cam hits overlap, It's going to be pushing exhaust back into the intake where it's going to sucked into nearest available cylinder that's on the intake stroke. Built in EGR is as bad cylinder pressure loss, but combine the two and you've got a real slug... although it's not absolutely necessary, I myself would also be upgrading to some three inch exhaust too.
But aside from all that, I'd still like you to run a compression test and log the numbers for yourself at your convenience. Always good to test and log what you have with a fresh engine in case you have any trouble in the future. And oh yeah, definitely a great looking ride, I'm sure we'd all like to see some more pics!
:thumbsup: