Overrun air recirculation control, overview

The following list pertains to Fig 1.

1. Front air intake pipe 
   • Pressure side of turbocharger
   • Before throttle valve
2. Mechanical air recirculation valve 
   • For turbocharger, cylinder bank 1 (right)
3. Non-return valve 
   • Note installation position: arrow on housing points in direction of flow
   • Located below intake manifold
4. Vacuum connection 
   • At bottom of intake manifold
   • Supplies vacuum to Recirculating valve for turbocharger -N249-
5. Turbocharger 
   • Cylinder bank 1 (right)
6. Rear air intake pipe 
   • Intake side of turbocharger
7. Turbocharger 
   • Cylinder bank 2 (left)
8. Recirculating valve for turbocharger -N249- 
   • Testing, see RECIRCULATING VALVE FOR TURBOCHARGER -N249-, TESTING 
9. Mechanical air recirculation valve 
   • For turbocharger, cylinder bank 2 (left)
10. Vacuum reservoir 
    • Fitting location: in front left wheel housing behind wheel housing liner
Fig 1: Overview Of Overrun Air Recirculation Control System
Courtesy of AUDI OF AMERICA, INC.