Success today. The wiring was correct, so the only possible remaining item was the butt connector. I replaced this and...hey presto...the system jumped into life. I just hope it keeps working - the circuit now has several connectors where I had isolated and reconnected stuff and I have no more butt connectors left.
Flush from my success, I used a syringe to test the ASI and the altimeter (both the steam gauges and the indicators on the EFIS). Both showed rapid leakage at high/low pressure, but this decayed exponentially as the pressure neared the local pressure. I'm not sure what to expect. I'll need to ask the experts.
More work on the replacement flap lever ensued. The replacement is tidy, but I had hoped to reduce the spring pressure somewhat, but I'm not sure this will be easy. Certainly not obvious to me.
I managed to sign-off some more inspection items today.
