Review on K&N Cold Air Intake Kit for 2001-2007 Chevy/GMC Heavy Duty 6.0L V8 (Silverado 2500, Silverado 3500, Sierra 2500, Sierra 3500), 57-3031-1 - Enhanced Performance and Increased Horsepower by Daniel Morris

Throttle body sucks air audibly. Complements the Gibson headers and Borla exhaust header on my Chevy Silverado 2500HD '03. I immediately noticed the ease of pedaling as my engine is now breathing really well. I also chose to purchase a dry loader pre-filter to protect the filter from moisture and the filter itself from having to remove dirt from the crevices. The water collects in bubbles and simply rolls off when drops hit the dry pre-filter cover. Sounds like a big block from 8.1 as it absorbs much better now. I dropped a K&N filter before installing the intake kit and still noticed how much better the airflow is now. You don't need to cut the fan shroud. Remove the Vortec cover over the engine and slowly work your way down the pipe leading to the throttle body. This continues, giving you a finger and a half clearance from the radiator fan. You just have to have a little patience.