Pulling V.A at idle

The only time I've tried to Tune er, was when I first started Streeting as a Daily Driver.. found an Article on FBBO, using a vacuum gauge, about 2500 Rpm, then bringing the screws in till highest idle, + best vacuum
Unfortunatelty thats misleading. Using the vacuum as an indicator of power can be useful, but only certain situations. For example, Given the same rpm, same throttle position, and same load. There is no load in park (and neutral) other than engine friction (and driving the transmission pump). An engine can be run extremely lean when there is no load. Lean is less dense fuel-air mix and therefore slower flame development, needing more time.