Here's how the resonance flaps work on my car;

The valve in the crossover pipe, I'll call X/O, and the valve in the manifold itself, I'll call 3/6.

The solenoid for the X/O valve is connected to the Yellow / Brown wire pair, and is the upper of the two solenoids when in the as installed position.

The solenoid for the 3/6 valve is connected to the Grey / Brown wire pair.

In the relaxed position with no vacuum, the X/O valve is closed - i.e. the crossover pipes remain independent for their full length.

With no vacuum, the 3/6 valve is closed, and the manifold behaves as an independent pair of 3 cylinder manifolds.

<2400 rpm 3/6 valve Closed, X/O valve Closed

>2400 rpm &
<3500 rpm 3/6 valve Closed, X/O valve Open

>3500 rpm 3/6 valve Open, X/O valve Open

I didn't reliably obtain any switching above 3800 rpm as has been suggested elsewhere, but, for me, that's quite academic; it's not an area of the rev range that I use often, or for any duration.

The sequence above seems logical enough, and so, I'll have to look elsewhere for an improvement in fuel economy. Perhaps I should just drive a little slower?