Here's 3 sets of data on my car (APR Stage 3) which show the following combinations of Airbox Hole Mod and Filter:
  S4 Lower Airbox Filter Temperature
Dk. Blue Stock OEM Audi  
Orange 3" Hole OEM Audi  
Green Stock K&N Cone 48F
Red 3" & 1.5" Holes K&N Cone 58F
Lt. Blue 3" & 1.5" Holes K&N Cone 42F
Pink Ram Air K&N Cone
56F
The ram air headlight replacement is always as good, if not better in flowing more air, espicially at higher RPMs/Speed.  All graphs are of 3rd gear.

Zoom from the above graph:

 Trendlines of the data:

Zoom of the above trendlines: