Thanks for the web link. It's very helpful.

If the schematic shows the valves in their correct orientation relative to the engine, then that's how I currently have the pipes plumbed in.

I've searched the site for resonance valves, without finding anything appropriate - does anyone know how and when, under what engine operating conditions these resonane valves should operate? I'm thinking of running some thin wires and leds, so I can tell when the vacuum solenoids are energised, but as yet, I wouldn't know if they were working correctly or not.