2002 Chevy Impala Catalytic Converter

I wouldn't jump to that conclusion, but he may be right. You need to have the car in a position that you can access the exhaust, preferably on a lift.

Look for black areas at joints, the exhaust manifold, converter etc. Carbon escaping with leave that trail. Without touching the system, feel for escaping exhaust pressure form suspected areas. Use your ears to narrow it down first.