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 Fernando Ramani

Worth every penny. Be careful before cutting the fan cover, it may not be necessary. I was almost ready to cut mine and tried again at different angles and finally found the right one that fitted the throttle body perfectly and I didn't have to cut anything. Installation took 15-20 minutes from start to finish. I have a 2006 Silverado 2500HD with a 6.0 liter petrol engine, I got about 1mpg but every little thing counts!