[Paul Workman]

Hello, and welcome to the ZR-1 madness!!

Sounds like your nibbling all around the idle issue. And, I could be wrong (and I apologize if I am, but I caution ya on (what appears from you post to be) throwing parts at a problem w/o really doing the "due diligence: "Never assume!"

Barring a bad check valve in one of the pumps, the very small leak down results you have - tho not ideal - wouldn't likely cause an idle issue or missing @ low rpm, IMO. Loosing several psi over a minute could cause problems, but usually is accommodated with other signs, e.g., fouled plug(s) and disparaging BLM results (balance).

You need to scan it and see what is the big picture. You'd be interested in what the O2 sensors are doing - are they working and are they balanced?
The BLMs will tell you if you have a fueling issue on one bank or the other (or BOTH). Are the cross counts reasonably the same or is one or the other sensor "lazy" (one O2 w/ 1/2 the cross counts of the other would indicate the sensor was well on its way to the trash barrel!)

Reading the plugs can give you a clue to whether a particular cylinder(s) are running rich or lean.

Is the injector dwell time on the two banks uniform?

Dominic (aka XfireZ51) recently wrote an interesting article describing the effect (or LACK thereof) injector flow abnormalities has on idle and low rpm response and over all drivability.

Food for thought!