Hi again all, I'm still alive! Been busy so not had time to tinker much less take pics or update on the damned bike.
Anyway, had a bit of free time this last couple of days so pulled everything apart once again, stripped out the hacked up wiring loom & all. Went back over the intake boots, damn sure no leaks there now. Re-hashed the tweaked TB's using the ball bearing method outlined above (thank you TMG), cleaned up a lot of other random bits & reassembled.
On reassembly I've now switched to the un-chopped loom which was, supposedly, from a K100 but there's only 3 coil plugs and 3 injector plugs on the (also different) EFI harness so it's evidently been misidentified by the PO. Also swapped over to the other HES that came with the bike ... Anyone get the feeling this is an issue that was being chased prior to my ownership? think Although I did find an issue, the tone ring was loose on the crank?/balancer? so tightened that with some blue goo on the bolts. Maybe that was it?
So onto one of the non duplicated parts in the basket of this case, I know a few cars around this era have issues with bad capacitors in their ECU/ECM so opened up the brain box. Nothing doing in there. I only saw one electrolytic, a 220@40v which I've swapped for the sake of it even though it actually tests good ESR and capacitywise.
Since I now have the appropriate plugs, I got into the clocks & gave them a quick clean up to see what works/doesn't. They're full of corrosion but most of the warning lights and backlighting works as does the tach (speedo not tested yet).
BUT... After all of this I still have pretty much the same issue I ended up at when I gave up on the original harness, in that it'll now start pretty well cold, idle along nicely around 1300rpm & even responds to light blips of the throttle with only a little lean pop if I'm too eager. Then, as she warms up it's as if someone's flicked a switch & it just dies out lean. I can just about get it to idle if I hold the starter button (slight enrichment) or better so if I wedge something in the AFM to trick it into believing more air is entering hence more fuel. Kind pf stopping to think things through now, suggestions welcome lol
Oh, and I've also checked the coolant temp sensor, it's in spec and stays in spec when bike is acting up. If I install the ratty old AFM (which I've been tweaking on) then I can get better results than with the unmolested one, although that produces a hugely rich idle in exchange for enough juice to run on throttle & that results in fouled plugs after a few minutes playing.
I'm beginning to wonder if valve clearance is an issue although I did check by eye and they all have clearance, compression sounds exactly the same on cranking etc. I've even blocked off the PCV on the plenum and vented to atmosphere to rule out excessive blow by messing with the AFM (doesn't seem to be any more than I'd expect). other than that though it "feels" electrical to me & I'm wondering if an ECU or Ignition module fault might cause this sudden switch on warmup from running reasonably to just refusing to deliver enough fuel without manual intervention.
Edit- thinking a moment, I may as well pull the injectors and clean them up again & rig something to measure fuel pressure just in case the regulator or pump are crapping out as they warm up. Cheers all, will go scratch my head at it some more lol