Manifold pressures should remain fairly constant across the manifold with each runner varying that wee tiny bit with intake pulses. Those pulses should be the same values for each hole unless you've torched something important.

What screws up throttle body style injection systems are full height plenum dividers. That creates an irregular vacuum signal to the sensors in the throttle body. Cutting down the divider or using an open carb spacer stabilizes the signal, just like with a carb.

and I've had very good luck with an rpm performer intake on my turbo efi 383 with a sheet metal elbow and forward facing Ford style TB.

The low divider of the RPM and that long elbow would straighten out any signal bouncing off the throttle blade. However, it would make for a train wreck if you were squinting fuel all the way up there.