I have the same problem with my 1993--136k miles. In my car it is a cracked rear exhaust manifold. I have come to learn that it is very expensive to repair (8-9 hrs labor) since the rear side is very difficult to get to.
I am perplexed because it otherwise runs fine as a car for my teeanage son, but I really hoped that I could get many more miles. It likely not worth the $1000-1200 to spend at this juncture of car's life.
Any thoughts?