I wish I could have done a good baseline of fuel mileage beforehand to give a comparison. I can say without question though that the throttle response in the low RPM range has been improved. Those first moments as you are pulling into traffic waiting to hit that 2K+ rpm mark so you can start getting positive accelleration used to seem like an eternity, now that sweep of the tach through the lower section of rpm's takes less time for sure. Above 2K I do not feel any tangible difference in the cars performance. I wasn't anticipating any benefit here though other than perhaps less wear on the turbo.
It may be only a horse or two, but it was cheap to do and will be there for the life of the car. If it gets me even 1/2 of a mile more a gallon of fuel it will also be worth it because it only took a few hours and will be there for the life of the car.
Eric Z
P.S. I did a test with the hose today spraying the front of the car aggressivley with it running and no water got sucked into the air box.