I solved the engine noise problem by wrapping the tube header with a Thermo-Tec header blanket. I also wrapped the straight pipes between the converters. This reduced the noise by about one third. It still has a nice growl but without the high pitch. I didn't wrap the converters figuring the don't echo much ( I could be wrong there). In retrospect I would have wrapped first with the fiberglass tape for headers then put on the blanket. An after market header double wrapped would be great. I figure my Corolla makes just a little more noise than a Camry 4. Since V6 engines have a header by the firewall, I think Corolla's main noise producer is the tubing exhaust manifold. Hope this helps.
