Water mist “injection” at the breather…good, bad or worthless idea?

Driving daily in a normally hot, arid climate like Tucson, AZ, even after turning out my idle jets to enrich the fuel/air mixture, retarding the timing to -15 degrees BTDC, and purchasing 91 octane petrol when affordable, I'm oft plagued by knocks when accelerating, especially in the heat of the day.

By contrast, when it rains, Mathilda acts like Chuck Berry's "Maybelline" and I suspect for the same reason: a slight addition of water mist to the fuel/air mixture cools the air down,...

Water mist "injection" at the breather...good, bad or worthless idea?