I'm not (directly) adding gas, but I am directly adding air by opening the throttle valve. So, my 14.0 - 14.5 AFR at cruise immediately gets leaner when I open the throttle. I'll hit 15.5 - 16.0 AFR trying to pick up speed
This is not right.
Anytime you move the primary throttle valve, you should have a near-instantaneous increase in fueling to match the change in cfm. It's your job to make it so.
"Lean is mean" works at the racetrack, maybe.
But on the street is causes too many headaches. A tad rich will respond better to quick changes in throttle inputs, with fewer hesitations, and makes you feel more connected to the power-curve. Oh and you can run a lil less pumpshot, which has a dramatic effect on city fuel-consumption.
A lean cruise is OK, within limits. But if you go too lean, then your plugs will get hot, and when you come in off the hiway, you will get that sickening feeling that something is wrong,lol. Take a breath; as soon as the plugs cool off, throttle-response will return to normal. This sucks for passing tho, cuz you gotta wait for the plugs. I don't like it, so I don't run that lean.