I got turned away for my filter once, they let me go change it back to stock before doing the test. They said it would fail right off the bat unless there was a CARB number on it. Maybe they were just being overzealous?

97 Contour SE MTX K&N 3530, UR UDP, 19# Injectors, mystery mod, FMS wires, Fordchip.com chip, SVT: TB, Flywheel, clutch, exhaust 04 Grand Caravan SXT