Honda Throttle Position Sensor question

[steer_rally]

I've been trying to investigate engine running problems - erratic idling, vibration, hesitation up to 3K revs (pulls like a train above 3K), "hunting" at constant throttle and popping/backfiring on over-run. There doesn't seem to be a vacuum leak (WD40 sprayed around carb rubbers has no effect). Plugs are all new & gapped, and are a nice light brown colour. Air filter ok, could be cleaner but not too bad. Carbs have been balanced.

So local bike shop/garage suggested I check the throttle position sensor. Everything checks out ok - correct voltage getting to the tps, resistance increases/decreases as I open & close the throttle, and resistance as measured from the ignition module is within range.

So all seems ok there. BUT. According to the Honda manual I've got, if i disconnect the plug from the TPS, start the engine and take it up to 3.5k revs, then re-connect the TPS the revs should increase. Nothing happens. Basically there's no difference in engine performance, idle, or anything else as far as I can tell, whether the TPS is connected or not.

So now I'm baffled, as the TPS doesnt seem to be doing anything at all. Granted, I'm not sure exactly what it should be doing, presume something to do with fine-tuning the ignition timing? I know if I disconnect the TPS on my car the engine just stops completely.

Any opinions?

Apologies for the long-winded post, but any suggestions much appreciated!