<Audi> Help! Intake leak

[Steve Manning <stephenm@ix.netcom.com>]

My 1990 200tqw has suddenly developed what seems to be a huge intake leak
under boost.  At boost over a couple psi (around 1.1 bar) it starts making
the loud metallic hissing sound (at least it covers up my fuel pump noise
<grin>).  The normal suspects (Michelin man hose; WGFV hoses, etc. etc.)
all seem to be fine (I pulled them and checked for leaks).  Waving around
propane at various hoses under the hood to find a leak turned up nothing.
The idle screw in the intake manifold (above the Michelin man hose) is in
place.

Other symptoms: higher than normal idle (although it is steady).  When
letting off the throttle under boost, you get a weird 'hiccup'; the
drivetrain jerks then smooths out (almost like feeling a harsh auto trans
shifting gears).  Boost is slow to spool up.  I first noticed the symptom
after backing out of the throttle after hard acceleration to 70mph (merging
on an interstate). Under gentle acceleration things seem normal, however.

What else should I check?  Wastegate?  Or could I have blown the
intercooler?  I checked the intercooler to see if I had blown off the side
tanks, but visual inspection and yanking at them didn't reveal any
weaknesses.  The clips seemed to all be there.  I figured the tanks would
have physically moved, but is the normal failure more subtle?

I appreciate any help.  I need to drive this car for a 5-hour trip up to
New Jersey on Wednesday, so I've got to get it fixed ASAP..thanks!...SLM

Steve Manning:  stephenm@ix.netcom.com
...Physical home: Metro D.C. area, USA
.....Virtual home:  http://www.stationwagon.com