Thanks for the nudge! and continued interest, sadly it's not a commercial job for us, we have paying customers to deal with
We'll try and get a look at lunch time or late tonight, but the ability to have some thinking time is no bad thing, rather essential actually, although while there are further tests we COULD do,
Not had time to read all the replies and digest them still, as pretty busy, but had started this post a while ago, so I'll dump it here, as this job is a good fit ... bear with me ...
I'm not sure if this was a commercial job if we would do that many more tests, more likely we'd strip the inlet and inspect, as we'd get answers (good or bad) of a more conclusive nature faster ... and could still do a compression test with the cover off (concern over injectors might not get good resolution though).
One caveat, that if we thought we MIGHT learn something to help us in future diagnostics of other cars, then we MIGHT burn some technician time to see if there was a learning outcome to be gained (you've got to speculate ...) ... but sometimes we don't have the time or the client wants immediate answers, so speculative testing is not always possible.
We will try to fit in some tests, as I've got a few ideas based on my own thought's, STC's and the other input from here, which is both excellent and really appreciated. Thanks to all again. BUT no promises, a young man is without wheels, and the fastest repair might not align with the inquisitive side of my brain or the clear interest here at the Forum
Also to note, on a commercial basis, sometimes it's pragmatic (maybe this is cynical, but life's lessons teach you to protect yourself) to not spend effectively unrecoverable hours testing and diagnosing the fault completely, as once you've done the hard work, sometimes the customer will turn around and say, thanks, but actually my mate (substitute incompetent previous garage/beer buddy/google grease monkey/forum gorilla/...) says he can swap xyz for half that ... and as you've not undone much he's happy to take it on!
The xyz is often only a symptom, but the owner never heard that, well not much between his ears for it to stick in, and you get the blame for mis-diagnosing the fault ... sometime better, even if you have got a fairly good idea of the fault, with proof, to still say you need to strip the car to prove your suspicions, confirm the damage and the root cause ... being too clever often does not pay.
Oh, the reason for the moral lesson (not that I'm qualified to lecture, so this is all IMHO, no offence or egg sucking intended), is that except a compression test to prove under or excess pressure, and/or an injector swap to confirm not a leaking injector causing fluid to accumulate, there is not much that can economically or usefully be done (well I'm sure a few purists would disagree, and so might I), but over testing is sometimes as bad as undertesting. I've encouraged myself to overtest many times (sometimes for learning outcomes, some never obtained)...
But yes will post back further test results and when we strip it (hopefully some pictures too), but thought it time to also ensure people don't loose sight of the real world goal (worst offender sat behind this keyboard! I'm imperfect, go figure)
Our job is not purely to diagnose, or play with scopes, there is a very real need to be commercial and pragmatic, I'm just reminding myself first and foremost, and letting others know to bear it in mind. I hope you can either have a laugh, bear it in mind, or ignore it without offence, as none is intended.
And don't let this stop further ideas coming forwards, all still welcome and will get due consideration, I'm still a curious inquisitive nerd at heart