quote] I did say it's good to have for fine tuning.[/quote]

And the tune will change between a full tank and an empty tank. Unfortunately there is no “automatic” prop valve.

Many drag racers put the valve in the front brake line. An average street car should have it in the rear line. Race cars - other than drag cars - will have two masters with the bias adjustable in the linkage so adjustment can be done on the fly as conditions dictate.