I reconfigured my vacuum/boost lines today so that my wastegate is hooked up to the intake manifold like the official Prodigy setup. I'm still getting 8 psi, so there is not a 1 psi drop across the throttle body to explain my 8 psi vs Snarf's 9 psi. Now I'm just waiting for NOLA's results after he sets up his wastegate properly.

One more piece of the puzzle. I'll be switching back to my setup, now that I got that info.