Look at Catco catalytic converters. I used one a V6 4.3L engine. The Jimmy had a Magnaflow muffler. After adding the high flow converter, it was even louder! It had a nice rumble. Sound really woke up above 2500 RPMs. On a V8, it would be super nice.

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'06 X5 3.0i - bought @143,123 miles (12/26/20)