Swap out the dirty factory air filter in your 1999-2003 Ford 7.3L Powerstroke with a high-quality Drop-In Air Filter. XDP carries drop-in air filters from manufacturers like S&B Filters, AFE, K&N Engineering, so you can find the best one to meet your vehicle's needs. In most cases an oe-style drop-in air filter will be made with paper filter media, where an aftermarket air filter typically features a synthetic media, or a cotton gauze design that may be dry or oiled. The air filter is a critical component in your vehicle and is designed to keep dust, debris, and contaminants out of your engine. Drop-in air filters get their name from their designn as most have a "drop-in" installation and simply fit inside the factory air box.