[200q20v] hesitation, hiccup revisited...new clues

[Tresturbos at aol.com]

Hi list,

A couple of months ago I wrote about some hesitation or jerkiness under 
medium to low throttle at no particular point along the rpm band (not just 
down low, I ain't no lugger :-)

While away on vacation, I left it with an Audi/Porsche mechanic.  All they 
could come up with is that the roughness was typical for a manual 
transmission Audi, especially at low revs.  When I told them that it was not 
at low revs, but rather during 3-5k rpms, they didn't have an answer.  They 
had checked the O2 sensor and the plugs.  Nothing looked fouled-up.

Over the past few weeks, I've paid close attention to the conditions under 
which the hesitation occurs, and have noticed that it is accompanied by a 
muffled metallic sound emanating from the rear of the car.  I believe it is 
at the rear passenger side.  It's almost like light metal on metal contact 
that sort of flutters when the hesitation occurs.  There's definitely a loss 
of power that accompanies the sound.  It seems to happen anywhere between 
3-5k rpm, yet doesn't seem to correlate directly with rpm as do many exhaust 
buzzes.  It does not occur under wot or near wot.

Under load and throttle, I hear another sound that two mechanics have 
suggested to be due to a worn center load bearing.  The drive shaft touches 
the exhaust.  Apparently a new bearing would lift the drive shaft up and away 
from the exhaust.  I'm planning on saving this replacement for when I 
eventually replace the exhaust.

Anyhoo, any ideas about the source of the hiccup would be greatly 
appreciated.  Maybe it would help in directing the mechanics to the problem.  

TIA,

Mitch Frey
'91 200tq IA Stage 3
'00 A6 2.7T