bigger injector means the injector pulse is shorter. Short pulse with an even smaller injector means lean mixture out of the box. The PCM will try to compensate for it up to a point. Guys on LS1Tech are saying their fuel mileage is going up when they install much larger injectors. maybe it has something to do with the fact the the fuel vaporizes better with a shorter bust of spray rather than open a long time relieving pump pressure.