Originally Posted by HP Autowerks
The stock airbox itself is actually the bottleneck, a very shallow box, both under and above the filter element. As GIAC has proven that the stock airbox is good at stock power levels, but at elevated power levels the intake is worth 7-10 whp or more depends on what kind of power(boost) you are making. In addition, the AFE intake is very efficient in back to back testing with or without it installed on the car, the power ouput stayed the same on GIAC's dyno.
What do you figure it's worth on a car with a stock tune and no other mods?