I have had an exhaust leak and didn’t know where until I went to the muffler shop last Friday. I could hear clatter like a valve so I figure it was close to manifold. New gaskets when engine was changed. Manifold to pipe gasket was cooked. Muffler shop said the pipe wasn’t true and to double gasket it. I did and it fixed the problem. Now, the car is running a lot richer than before. I can smell it. Is it related to the leak I had or a coincidence and something else? I guess my question is can an exhaust leak like that affect other areas?