simple: because its one hell of alot more than $5 more. The coupler alone is $15, the only sweep that Advanced Auto had is almost $60 (Spectre intake kit without filter) plus the $30 for the filter... with this setup you end up spending $4 for the coupler, 5 for the PVC pipe, and the $30 for the filter. I dont know about you, but i dont have $105 to spend. This setup works just as well and costs under half the price. (Prices acquired from Advanced Auto. Was just there looking at all this stuff less than 4 hours ago. There is no Pep Boys anywhere near here and i refuse to shop at Napa.)