Volkswagen: Secondary Air Injection system, vw dealer, air injection

Question
I have a 1999 (old version) Jetta Wolfsburg edition with 72,000 miles.  The check engine light came on (after I got it back from the VW dealer here who replaced the coolant flange) and the code was P0411.  I looked the code up and it said there is an incorrect flow detected on the secondary air injection system.  The mechanic wants to replace the throttle body at a cost of $900.00 and I was wondering if this sounds correct?

Answer
it is more likely to be a pipe off between the airbox and pump, or that and the intake manifold. otherwise it may be the air mass meter which is giving an incorrect reading and throwing the sytem out. i would not replace the throttle body unless everything else was checked and eliminated.