83 5kt stall out

[Tex Terry, II]

First - my thanks to Huw, Ti, Chris, Larry ( and others I do not remember
the names of) for the suggestion that I check the cat on my 83 5000 turbo
automatic (gas not diesel) sedan (not quattro) that was spitting hot
exhaust back up out the tube by the side of the turbo (CO test tube is what
I was told the tube is for when I asked about this back a few months ago
when I first came on the list).  I finally had a chance to remove, gut out,
and replace the cat (for testing purpose only, I will replace the cat now).
 After shutting down the car back in the summer of 1997 (because of the
exhaust spitting out the tube and the car not wanting to keep running), 
the car started up (after turning on and off the key three times before
each start, and going thru a cranking but not running condition for four
times) and ran for about 10 minutes last night.  The tube now had a little
suction to it and was not hot.  Then the engine started to want to lose rpm
from the idle mode and would not keep running, so I shut it down.  I am
thinking that the warm up regulator on the drivers side of the engine block
might be the culprit (I replaced the springs in it about a year before I
parked it).  The fuel is the same that has been in the car.  There is just
over half a tank.  The oil is the same and is reading full on the dipstick.
 The water in the catch tank for the radiator was still on the cold side. 
As I mentioned originally, I am really a novice to the Audi so please don't
leave out any small details when explaining.  I did get a Bentley manual
for this car.  Please tell me what other info I need to provide to the
list, so I can get help from ya'll to troubleshoot and fix the car.  I have
been reading this list regularly and I know that there is a lot of
knowledge and experience on here, so I am hoping that I will be able to get
some help.  I do not understand the meaning of a lot of the letters used
for phrases or names of parts, so please bear with me if I ask for simple
explanations.   Thanks,  Tex.