Strife what and how is the home brew 1st gear start? And Johnhef for the hole trick. That's helped eliminate the mechanical timing. The emissions being so good point away from that too: valves operating at the wrong time or spark at 180 should be knoticable. I thought perhaps dist could be off one tooth, but seems too close to right on. I would think that if a mechanical is causing this: one or both cams jumped a tooth or the chain stretched, it would cause a failure in emmisions. combustion could not be that good to pass nearly perfectly.

What I think I see:
An EZL that without vacuum can get put timing anywhere it is needed at idle, between 8btdc and 16atdc. That seems to be exactly what it should do with the sensor signal and R16.
A sensor that for the most part is catching the tdc at the right time, but I also see a temperature shift.
Both devices could change results with temp, but it is more likely EZL would respond linearly with a gradual shift in timing.

JMO FWIW: I would guess the sensor output would not shift in time but in amplitude (signal strength, amount, value, voltage) Its probably a coil that feels a magnet passing on the flywheel. It acts like a generator and responds with a signwave pulse as the magnet passes. the signal is probably a small voltage 0 to 1V, and that explians the shield on the cable to keep the low voltage signal clean.

If its output changes I would suspect it falls in volts and the EZL looses it in the noise and would respond with a window of irratic timing and sputtering or rough idle.

Lov this stuff,
Gary