[ItBites]

Jeff,

Injection will still flow fuel when manifold pressure approaches (or equals) atmospheric pressure. This will make more power, but maybe not a lot more.

The carb has to force the manifold pressure to be lower than atm in order to have the flow velocity required in the venturiis to drop the pressure and have atm pressure in the vents push the fuel out into the airstream. Sine the manifold pressure is lower than atm, the cylinder is not as stuffed and therefore less power.

Generally this will not make a lot of difference...