The K&N 57-1003 is a Fuel Injection Performance Kit (FIPK) for the 2001–2005 BMW M3 with the 3.2L inline-six. A high-density polyethylene (HDPE) rotationally-molded tube is paired with a washable, reusable High-Flow Air Filter featuring oiled cotton filter media. The kit also includes a heat shield that fills the space the factory airbox occupied. Shoppers searching for an E46 M3 S54 cold air intake, a 2001-2005 M3 FIPK, or a 100,000-mile reusable intake filter will find those details below.
Stock intake restriction is the main thing this kit targets. The manufacturer states the kit is guaranteed to increase horsepower and torque, and its dyno chart shows an estimated +17.83 horsepower. Owners on user forums are more divided. Some describe a throatier midrange and a stronger pull, while others report little measurable change and say that gains depend on the rest of the car's setup. The stronger case for this intake is sound, throttle response, and a filter you clean rather than replace. Compared with a cheap drop-in cone, the tube and filter are engineered as one system, and the manufacturer says the filter only requires cleaning every 100,000 miles under normal highway driving conditions.
Installation is a hand-tool job that most DIYers can finish in an afternoon. Start by disconnecting the negative battery cable, and write down radio and memory settings first. Then remove the strut tower brace, the lower airbox, and the mass air sensor, which moves into the new tube. Owners on user forums say the heat shield is tight to route under hoses and that the tube can be stubborn to seat on the plenum, so take your time with fitment. Keep the factory intake in case you need to return to stock, since the manufacturer's instructions recommends that customers do not discard factory air intake.
The manufacturer lists this kit for the BMW M3 with the L6 3.2L fuel-injected engine from 2001 through 2005. Confirm your engine code and model year before ordering, since the S54 engine is specific to the E46 M3.
The manufacturer states the kit is legal for use in all 50 states, so it is suitable for street driving in those jurisdictions.
The manufacturer says the filter only needs cleaning about every 100,000 miles under normal highway driving. Harsher conditions such as dusty roads or track use will call for more frequent cleaning.
Plan on roughly one to one and a half hours. The manufacturer's instruction sheet calls for a ratchet with an extension, 10mm and 13mm sockets, a flat-blade screwdriver, and a 4mm Allen wrench. The process starts by removing the four 13mm nuts that hold the strut tower brace. Owners on user forums report that the heat shield can be difficult to position under nearby hoses, and that seating the tube onto the plenum takes some patience. Dry-fit the tube and heat shield before fully tightening any hardware, and confirm the mass air sensor is oriented correctly in the tube.
