S4 advice wanted

[jwk@gcm.com (Jeffrey Kong)]

I am extremely close to buying a 1992 S4 with 33,000 miles for effectively $26K
including a trade on my 1992 BMW 325i with 44,000 miles. The S4 is emerald/ecru
in excellent condition.  I was even able to obtain the service records from the
VIN: owned by a doctor, regularly maintained including the 45K/2.5 year service
performed this past fall.  I contacted the original Wisconsin dealer who claims
that this was a typical lease purchase with the doctor turning in the S4 to buy
another Audi.  I intend to have the car examined by an Audi service department.
The only thing that I noticed that seemed at all odd, and I didn't get a really
good look, was that the engine seemed dirty.

It seems that S4's are somewhat rare -- I have discovered this in my month-long
search.  I would prefer a 1993 model that still has some warranty left, but the
choices are few (and more expensive!).  My questions:

1. Does this sound like a good deal?
2. What are the differences between the 1992 and 1993 models?
3. Are there things that I should ask the mechanic to check specifically?
4. Are there any known problems with this model?
5. Are there items that are supposed to come with the vehicle that I should try
   to check for, such as a toolkit, or a binder for the manuals, specific extra
   keys, special mats, wheel locks, etc.?
6. What are some not-too-expensive ways to boost the performance of an S4?
7. This would be my first turbo; are there special maintenance requirements?
8. This one doesn't have a CD changer; it is possible to put a non-Audi one in?

If my request is not appropriate, please tell me to get lost. Thanks in advance
for any help and or direction!

Jeff Kong
Wilton, Connecticut
jwk@gcm.com