Alot of the newer intakes I've seen lately also neck down like this one to 3" before the MAF. The K&N brand intake, Injen, Weapon-R, and AEM all use small mouth filters.

I don't understand how they think adding a big restiction to their design is supposed to help flow?
The best bet is to buy a MAF adaptor from CTA/BAT/SP Motorsports and a big mouth 3.5" filter of your choice. This way there is no restiction before the MAF.