Temporarily mounted the gauge (used one of those big black paper clips) without lighting......   

Doesn't take much throttle to get it down to 0.    And just a slight change in foot pressure to keep it above 10.   

Might have something here to improve mileage   


BTW,  there's another check connector in the engine compartment that's useful.    Single wire, round connector with rubber cap on it.    It's in the same vicinity as the 2 that are plugged into the fender.       It's a direct line to the O2 sensor.   So you can use a digital voltmeter as a cheap A/F meter for temp testing.     Readings jump all over the place when in closed loop mode, but become steady and high when in open loop......

With the voltmeter, I should be able to see under what conditions it goes into open loop, and the corresponding vacuum level.......