Would like to here from someone who has actually hooked up a vacuum gauge to a 454 mag mpi gen 6 and what was your findings how much vacuum did you have at idle.

I know this doesn't answer your question but if you can hook up a scanner you can read the MAP sensor and it will likely be around 45-55 kPa. This is roughly 12-15" Hg. For additional reference I've got a warmed over SBC Merc EFI MP platform that runs 48-52 kPa at idle with a somewhat aggressive roller cam.