So, given that I'm no longer embarrassed by my own stupidity (it's nice when you get there
), thought I'd update this as a cautionary tale...
Most of the symptoms continued exactly the same. Except, it also developed a new one where it would stop running entirely between 5-6K - exactly like ignition cut, all you could hear was induction noise - except you could get past it by using more throttle, and then it'd rev to red-line.
Which just seemed to make no sense at all. But it got worse and worse as the weather got colder. To the point where I became concerned about giving it close to full throttle, in case it suddenly pulled clean (which, luckily, it never did).
I looked at the TPS reset procedure, and wimped out on the grounds that you can only really do the first step without manometer, exhaust gas analyzer and something to read what the ECU is "seeing".
Booked it into Moto Rapido for them to look at it.
Decided on one last ride (it was a nice day). New symptoms: bike cuts onto one cylinder climbing hills, runs rougher and rougher until it dies. Bike will re-start and idle - but can't pull away, stalls letting the clutch out.
I can hear fuel in the tank, but pop the fuel cap to check - to see filler neck awash with rainbow-coloured water. Clearly the filler drain is blocked. Given torrential rain a couple of days before, dawns on me that the fuel is contaminated...
MR drain the tank, change the filter, put fresh gas in it, test-ride and report "bike starts and runs OK". To the point where they didn't even do the TPS reset malarky.
I'm initially a little skeptical. But I get it back and uh, yeh, actually, it really does....
Dammit... Talk about overthinking the problem, LOL... Drain tube must have been blocked for months, with every rain letting in more water - which of course, would just sit, trapped, at the bottom of the tank, no matter how much fresh gas you ran through it...