Guys trying to avoid the big-time federal fine associated with removal of a major polution device call the free flow cat a 'test pipe'. Every dyno study I've seen indicates no appreciable increase in power. Occationally If the ceramic element is cracked and causes an obstruction but the temperature goes up and your dash light comes on, or you hear cracked ceramic rattling around. I've always wondered why those determined but unconvinced individuals do not simply remove the ceramic element which holds the active chemicals?
1993 MB190e 104k