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How to Install a K and N Air Intake on BMW 525I

1. Carefully pry up and remove the alternator air supply tube and place it aside. Loosen the clamp securing the air intake tub to the MAF sensor and separate the tube from the sensor. Disconnect the sensor. Remove both front and rear mounting nuts for the air box assembly. Lift the air box and MAF sensor out of the engine bay as an assembly. Remove the clamp at the throttle body and remove the air intake tube from the engine bay.
2. Remove the two screws securing the MAF sensor to the air box and separate the sensor from the box. Remove the bolt securing the heater unit from the air box and place the heater unit aside. Remove the large o-ring from the air filter box and place it over the filter side of the MAF sensor.
3. Install the cone air filter over the MAF sensor inlet and tighten the clamp until the filter can only spin, followed by an additional 360 turn of the screw. Fit the small twisted bracket to the top of the rear air box mounting bracket and install a bolt, lock washer and nut. Place the longer bracket between the two air box mountings and install a bolt, lock washer and nut.
4. Install the stock intake tube to the MAF sensor and set the clamp into position. Position the thin end of the twisted bracket between the clamp and air intake tube. Tighten the clamp. Place the brass heater element into the hole in the back of the air filter and use an included zip strip secure the element to the twisted bracket. Connect the intake tube to the throttle body and tighten the clamp.
5. Lift the front of the vehicle and support it with jack stands under the sub-frame rails. Here you have to cut out a portion of the air grille. Measure and mark off at the half point of the right most portion of the grille. Cut out the bottom two horizontal rails with a knife or small saw. This should provide your with a one horizontal flat towards the top of the grille. Cut a small hole at the end of the cold air hose and zip strip the cold air hose to the cut out portion of the grille. Direct the cold air hose so that the air will be pushed towards the bottom side rear of the filter. Zip strip the cold air tube to the lower radiator hose.
6. Lift the vehicle off the jack stands and lower the vehicle to the ground. For a full customizable look, get a piece of chrome tubing about the same diameter of the stock intake tube and have it cut and bent at an exhaust shop to the same shape and length of the stock hose. Get two rubber couplers and 4 new clamps to secure the solid pipe to the MAF sensor and throttle body.