Changing the Idle air control valve on a 1999 Audi A8 Quattro.

Ebay Part, $40.  3 bolts (11mm wrench) 1 electrical connector.  Right on top of the engine, in front of the blower behind the intake manifold.  After installing I cleared the codes, but my error code came back almost immediately.  That's an annoyance.  I found another cracked hose.  Fixed, and cleared the codes.  Viola, no more check engine light.  Sweet.

Lesson Learned:  This car is CRAZY sensitive to vacuum leaks and reports them as the P1509 code.  Quintuple-check for leaks before dropping money on a new part