A stand-alone air filter assembly has a unitary molded plastic preform shell, with the preform shell including an inlet section, an outlet section, and a hose connection section integral with a downstream end of the outlet section. A filter media pack including a fluted filter media member is fitted inside the inlet section of the preform shell through which unfiltered air enters the air filter assembly. The outlet section of the preform shell through which filtered air leaves the air filter assembly converges from a larger, first cross-sectional area of the inlet section to a smaller, second cross-sectional area at the downstream end of the outlet section, and the outlet section includes one or more sensor ports that are each configured to support a sensor for measuring a characteristic of the filtered air leaving the air filter assembly. The hose connection section includes an annular hose bead interface formed around an outer circumference thereof for sealing engagement with a hose fluidly coupling the air filter assembly to an air intake on an engine.