Resonator delete on ml500
No real power improvement that I could detect, but it got a new nickname: "Deep Throat". (Nice sound improvement.)
As far as power is concerned -- nothing noticable, if any at all. But the sound is MUCH worth it!
I had my install shop do it for me -- it is simple to cut the resonator out and simply weld in a new (about 1 ft long) section of pipe. I suspect any muffler shop can do it with ease. Cost me $50.



