Hi again Sean, as you say the tandem pump would cause issues with all injectors & so i still think its an injector, there can also be some meaningful data on group 23 (beginning of injection point or B.I.P for short, which is the digital/ECU`s way of displaying what we would measure with a scope, the knee-jerk point of the current build section of waveform, similar to the wing-type pattern on a petrol injector when the injector actually opens) basically the BIP indicates to the ECU that the solenoid valve is fully closed/or in other words when injection starts, BIP should be as near zero as possible, the spec can be +/- 90 but the further away from zero, the more likely an issue has/is starting to occur, this can seem a bit confusing at times, especially as if say there is some air in the injector, the solenoid valve will close quicker than expected, the ECU can then register a fault code such as BIP below control limit etc.
Back to your issue, it seems a shame to stop now as you have tested beyond where many would get to & from here its just good engineering practices to see the job through, if you want to talk it over i am in the office tomorrow so can easily take a call 01334 850 259.
Remember; what doesn't kill us makes us stronger!
Regards, Phil.