Some more information about them from a different forum and also from a toyota setup and not an audi. However after looking online for a bit I did notice that BMW, Volvo,kia, and a few others have all used air assisted injectors at some point:
Toyota does claim air assist helps prevent fuel from clinging to the port walls, improves emissions performance, and also idling and overall engine drivability.
Since the older 2-hole non-air assisted injectors lack the air hole just before the injector nozzle, what you'll see, generally, is decreased efficiency and increased emissions - mainly in hydrocarbons, as there will be more unburnt fuel from the larger atomized fuel particles. This is the main reason Toyota's CA emissions 93-95 2JZ-GE adopted an air-assist injector specifically where the non-CA emissions 2JZ-GE did not. The 7MGE injectors will have a spray pattern consistent with older style injectors with less atomization and air-fuel homogenization.
You have to remember that the air assist is actually engine driven air assist (which is why there is a metering device). So, the air going through the air assist hole collides with the fuel particles in the stream just before they reach the 2 holes in the nozzle. This furthers the atomization and mixture of air and fuel even before it is injected into the combustion chamber with the accompanying intake air flow, resulting in greater efficiency. I still don't fully understand the concept behind the reduction of port-wall wetting with these injectors, but maybe someone else can explain that.
