1986 4000csq questions and such

[Dustin Wolpoff <melon@centuryinter.net>]

Hi, I am a 16 year old proud new owner of a 1986 4000cs quattro.  It has
146k and a good rust free body. The interior is pretty good.  I have
some basic questions.  First off, I know the CS on a 5000 means it is a
turbo.  Does it mean on the 4000 that it is a 5 cylinder?  Next off,
some mechanical and technical stuff. The car seems extremely powerless
taking off from a stop.  It does not have factory exhaust (previous
owner cobbled it together) and it just has one pipes back to one muffler
(I think there is supposed to be a mid-muffler in there somewhere that
is not).  Would this make it seem gutless (I think my 1986 Golf would be
faster at a stop sign), or is that how the car is?  It is great at
highway speeds.  When I engage the clutch, the is a big clunk/clank in
the rear and the tranny seems to shift around (I can feel it in the
stick).  Could this be a tranny mount, or if not, then what?  Anything
else I should check this car for real soon, problem wise?
Thanks in advance for the help.
Dustin