I don't have any manuals with me, but are you guys running a vacuum line from underneath the intake directly to the fuel pressure regulator? I forgot how that system is set up.
On the stock there is a threaded plug right after the tb on the intake as a vacuum port. When you use the port on the upper intake on the under side is the same vacuum. Thats what i was going to do with my performer before i sold it.
What I have learned over time, and my Dad has confirmed is that anything after the throttle body is running pretty much the same amount of vacuum. Thats where you want to run the line to. If you think I'm lying, then just hook a vacuum gauge up to different areas of the intake and show me a SIGNIFICANT change between the plenum and post-throttle body area.