It is smaller, I believe 2". Here's the thing though, I left the bottom on the airbox open for that exact reason. The sewer hose goes into the air box to help with cooler air. Sorry, I should have clarified.
(SOLD) 2003 Ranger 4.0L V6 FX4
2001 F150 Supercrew Triton V8 (DD)
2008 Fusion 3.0L SEL V6 (my baby)
1992 Taurus SHO MTX (my toy-almost Supercharged)
2004 Nissan Murano SL AWD (Wife's car)