How to Overboost APR Stage 3 for an A4

1. Open your A4's hood and locate the diverter valve next to the rectangular plastic air box in the driver's side corner of the engine compartment. The diverter valve is plastic and approximately 3 inches long, attached to the hosing that is also connected to the air box.
2. Pull the hosing out of both ends of the air box and replace the factory diverter valve with the N75 diverter valve, which is a larger unit used on different Audi models.
3. Insert the hosing that was connected to the factory diverter valve firmly into the N75 valve then close your hood. The larger diverter valve will facilitate the travel of additional boost pressure, thereby 'overboosting' the Stage 3 on your A4.