Originally Posted by RBYCC

I run twin Magnaflow spun metal high flow cats ( Random Technology knockoffs ) in my C124 M103-12V TT.
They don't use the typical brick catalyst like the OEM.
Very small, 4" diameter and about 10" long.

Picked up 11HP on a load dyno over a single SL500 OEM converter.

Inexpensive, about $110.00.

Changing the cat will not effect your exhaust sound.