Previous thread...
There was a thread about a guy removed the pre-cats and noticed an improved hp gain from the butt dyno. They are very heavy as well. It seems to be the concensus. Free up the cats and get rid of the resonator. I plan on doing this to my 500. Cat-back sysem (custom) with no resonator and a performance muffler. Good luck!
Shaun
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1992 Pearl Black 500E (08/91) SOLD
1997 White C36 AMG (T-Boned by Chevy truck) 
2003 Silver C32 AMG (lease due, traded up) 
2002 Pontiac Montana Vision SOLD
2007 Volvo XC90 3.2
2005 E55 AMG (newest ride) 
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