a/f meter in car using 110 octane

12.5 is in a decent range for WOT.

For cruise, 12.5, that's rich which I believe the coal lumps was referred. If the engine is in the 10's at WOT, it needs about 4 sizes or more smaller on both ends is my guess for WOT. Unless it's a turbo/blower car, then it's not far off on gasoline.

Swifter, start out by pulling 2 jet sizes front and rear and see what happens with MPH. Picks up, you went the correct direction. 12.0 is usually rich side for N/A engines. Don't jet to a number, let the MPH tell you if you are headed the correct direction.