ALong time ago I had to replace the cat on my 420SEL. I suspected a clogged cat because the car had no power. If you were to floor it, it would not go over about 50 mph unless u let off the gas and let it upshift. This was because the engine could not get over 5000 rpm. The car was also silent as could be. After many years with the new exhaust system (aftermarket), the new convertor started to deteriorate and rattle. Discusted at the idea of spending another $1000 on a cat, I guttet it instead.
As far as power is concerned, there maybe a little more. But I think it is just perceived as more power because it is a little louder and more bellowee(sp?). One thing I noticed for sure. The exhaust STINKS! Went on a road trip with some buddies, after a few miles they said they had to lead because my exhaust was so bad!! I also noticed that since i gutted the cat, I have alot more white smoke puff out of it when I start it up in the morning, and when i floor the car, it emits dark smoke. I think the cats filtered this out before. maybe there is something wrong with my motor where it keeps going thru cats, but instead of spending time and money to know, I took the easy way out. Hope this helps.
93 300D 2.5 Turbo, Black/Palomino 273K
09 E350 Black/Black 41K