Back almost to dynoing this motor. To reiterate, after switching the afx o2 meter on 8 to 7 I see a wild difference in afrs, bought a injectors flowing/cleaning machine, flowed and got injectors much closer, put two matching injectors in 7 and 8. Make a pull with afx in 8, 13.5 +/- in tq peak, 12.5+/- in hp peak, pull with afx in 7, 10-1 in tq peak, 15-1 in hp peak. Probe harness, power to all injectors stationary or running at same voltage within 1/10. Test with oscilloscope on both batches using msd tester to trigger a module, exact same wave pattern, repeat test with motor hot and running, same exact pattern, matches perfect, probe drive side and power side of each batch running voltage exactly same . Switch batch wires from 5 to 7, 7 to 5 and suddenly #7 numbers close to what 8 had, defies all logic since everything measures same. Unable to read what happens to #5 when I do this since I'm monkey fukking around swapping one probe cylinder to cyl and hadn't welded a bung in #5 yet. In this same time frame I trip in shop and dislocate my right shoulder.
At this point I step up my game, buy a Daytona 8 pak o2 system and a 2 channel Daytona portable o2 tester for in boats/cars that will match. Older depac only has 2 o2 channels available so I buy 2 analog reference boxes from Innovate that will convert the other 6 channels of o2 data , tach signal and 0-100 fuel supply pressure that I will be able to moniter and log on my laptop, will be finished and doing further testing soon, Smitty

I also built this swinging arm to support cables to sensors and welded o2 bungs in left handed (Im right handed)

Very thorough, nice.

I wonder if the injector driver in the ECM is the issue.

I thought that too until I flashed a spare mefi3 ecm and nothing changed. What baffles me is the injector wave form, voltage etc being dead identical. It seems to still be the harness since things changed when I switched batches between 5 and 7, I'm dying to see whats going on in number 5 cyl I will know soon once we finish the 8 o2 sensor setup, we only have about 4-6 hours of work left BUT I work full time outside of my shop plus work 40 hours there, My son works 60+ hours a week for me and we are doing a Cam, intake, rear end upgrade to a customers Camaro, a trans in a 07 Dodge diesel truck, a 2000 ford super duty trans, 2 TH-400s going behind big power plus flowing injectors for customers, welding etc so finding the time right now is hard with everyone screaming for their cars, trucks and transmissions! Oh, and my wife bought tickets to Florida for 5 days starting Saturday 6 months ago (I would MUCH rather be in shop during those days off!!)

8 pak o2 sensors now working, pulled motor at wot at 3000, 1 bank of 4 cylinders at 13.5 to 14.5, 1 bank at 10.5 to 11.5, clearly a problem with electronics, swapped 5 and 7 injector plugs, pulled again to 3000 and held it at wot, 7 switched from 10.8 to 14.2, 5 went from 13.9 to 10.6 , changed harness and repulled, no changes, already swapped ecu with no changes. Its clearly a problem with electronics but running out of things to try.

Maybe an issue with your exhaust system radically reducing flow on one bank? Fuel pressure good at both rails?

I'd be inclined to pull intake and put on a single plane w/ a carb and see how the engine responds.
may want to look at the 12v supply to the injectors,maybe a high resistance in the wire/connections.plus recheck those grounds,make sure theres no ground loops on the ecu's ground.
had that problem many moons ago on a fast system a shop couldn't get started.that was a fun one to chase.especially having to work under the dashboard.
good luck,keep us posted.

Converted this back to single rail when i assembled it this year. The injector batches A and B ie "batch fire" consists of 2 cylinders on each side, 1467 and 2358, i can switch injector trigger wire between cyl 5 and 7 (2 different batches) and make afr change drastically, not mechanical, not fuel pressure, comes down to electrical issue thats elusive

In florida now till wed BUT did swap harness and redo grounds friday and make some pulls. Problem remains same, have just about tried everything. When i say "bank", i really meant "batch". To re-iterate, i can pull motor to 3000 or 3500, hold it on dyno brake at wot, #1 cylinder will be at 10.5, #3 will be at 14.5, #5 will be at 14.5, #7 will be at 10.5 (give or take a tiny bit). Then,switch injector lead from # 1 to 3, 3 to 1 ( both on different batches), do same for #5 and#7 (both diff batches). Make same pull, now#1 will be mid 14's, 3 will be mid 10's, 5 will be mid 10's and 7 will be mid 14's. It definatly follows the batch wiring which rules out anything mechanical, air distribution, fuel supply etc.
Now that i swapped harnesses, ecu (injector drivers), watched injector pulse wave form and supply side voltage from both batches on dual channel oscilloscope under a load theres not much left. The only other thing i thought of since friday is to swap ALL the injector leads batch to batch and see if problem follows from batch to batch on all 8 cylinders.

Is the interval between each batch firing the same?