Swap out the dirty factory air filter in your 2004.5-2005 Chevy/GMC 6.6L LLY Duramax with a high-quality Drop-In Air Filter. Drop-in air filters are aptly named as they have a "drop-in" installation that allows them to fit inside of your factory air box. Find drop-in filters from manufacturers like S&B Filters, AFE, K&N Engineering, and others at XDP. The air filter is a critical component in your vehicle and is designed to keep dust, debris, and contaminants out of your engine. Most factory-style drop-in air filters are made with a paper filter media, and aftermarket performance air filters generally use a cotton-gauze media that requires filter oil, or a synthetic dry media.