turbo bypass valve

[Brandon Rogers]

Hi all-
I believe I need a new turbo bypass valve for my '98 A4 1.8Tq.  I get a
gulping/humming sound for a moment while accelerating, or sustained at a
certain boost level (but I don't know which-no gauge).  I hear the likely
cause is the TBV.  My car is chipped.  Can somebody please help me with a
part number for the turbo bypass valve, either for the A4, or I hear the TT
TBV will work and is better.  Also, where exactly on the car is the TBV
located--I've identified 2 parts and I'm not sure which is which.  Greatly
appreciated!

Brandon
'98 A4
'84 urquattro