[Phantom]

The only time that I see this possibly helping is on a cool start when the fuel is warm. The reason being is faster flame front helping completely burn the mix adding a little power calling for the IAC valve to close a bit more while maintaining idle rpm.

The only other way I see it helping is in OpenLoop since the car ignores the O2 sensor but you would have to reprogram the PCM to tell it that there is less incoming air so It will inject less fuel, but that will work with out the jar.