After having my fuel pump replaced, my car was running really sluggish, had massive power loss and ran really terrible. I found out that the problem was clogged catalytic converters. Apparently the filaments inside were tearing apart. My mechanic informed me that he cleared out the debris and clogging and told me the car was good to drive. The check engine light is back on and the cats produce a spurting or "putputputputputput" noise on idle and make more noise upon acceleration. I also smell exhaust fumes every once in a while. Any ideas on what to do now?