Recommended Procedure
WARNING: This page is about a different car, the 2008 Ford Pickup, 2008 Ford F550 Super Duty, 2008 Ford F450 Super Duty, and 2008 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
Inspect the air cleaner inlet and ducting to verify no blocks or collapsed ducting. Inspect the air cleaner housing and filter for proper installation. Inspect the air filter restriction gauge to make sure the indicator is in the normal operating range. Inspect the exhaust system for damaged or blocked pipes.