My Audi with 10hp

[Festively Jolly]

Well, picking the 1988 Audi 90 FWD for the... gee what is it now 7TH
TIME AT THE MECHANIC!  I pick it up  and idle to the stop sign which is
about  feet away from the lot.  So i try to pull out in traffic and i
had a new bhp of about 10-15hp.  Almost getting hit about 3 times i
pulled it right back into the mechanic.  He drives it and i look at his
puzzled face and then the temp light comes on.  
   It has been in the shop about 3 times for the cooling factor alone.
   But back to the subject the mechanic pulled it into the garage and
told me "the engine is starving for air"  maybe your timing belt". Well
i had that put on about 30K miles ago. "Ugh might be your air filter".
Well i had that put on a short while back and it was very clean.  "I
think your eXhaust is clogged... maybe a bad cat".  OK the car was
perfectly fine 3 days before.  He popped the hood and revved the
throttle.  steam shot out of the radiator reservoir.  It made  this new
sound (neat none the less) like it was a tuned civic.  So the mechanic
cant figure out the problem. Can any of you help?  THANK YOU ALL SO VERY
MUCH.