It's inches Hg not mm, but IIRC 15-16" at idle is about what my car shows.

Duke

I just replaced my cat on my 560SL with an aftermarket $440.00 vs $4000.00 for a genuine MB. There is a HUGE difference in Weight and Quality between the two. In fact Im so discussted with the DEC cat and Miller crossover pipe I got that I am saving the old MB one to do a full repair on the heat shielding and that they will be put back in when the new ones wear out, which Im sure will be soon. The MB unit is non-magnetic stainless the replacements attract a magnet meaning steel or low grade stainless. The cat size complared to the original MB is tiny. I also belive that I will lose a significant amount of performance with this setup and that the system will be significantly louder. Basically If I had known this was the S@#$% I was doing to get I would have gone to a custome exhaust place and had something realistic made up. Aslo all of the pictures I see of the DEC cat for a MB 560SL are pictures of a genuine MB unit not the DEC cat itself. From all I have read DEC was the most highly recomended of the replacement Cats, due to its mandrel bent tubes, which the Miller crossover pipe does not have, But from what I can see thats not saying much.

John Roncallo