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  1. #1

    Default Hollowed out Cats

    I was thinking of hollowing out my cats. Has anyone done this and did it make a difference? If you did this and it made a difference how did you do it? A friend hollowed out the cats on a Duramax and it made it sould pretty healthy and he claims it made a difference.
    Mike :fighting0037:

    2007 GMC Sierra Z-71
    2009 Chevrolet Malibu

  2. #2


    Trying to fool the stock engine computer into thinking you still have catalytic converters? You wont be able to do this without a custom tune. How many miles you got on your cats? Are they bad? This could be an expensive mod if you don't have a back set of catalytic converters if something goes wrong. Hopefully if you do this you will have a tune that deletes both of the rear O2 sensors. I once bought a cheap set of headers that came with the off road pipe. Of course the system didn't have cats so that's why it was cheap. I put headers and off road y-pipe on and after 10 mins my truck ran like garbage! Maybe with a good tune I would have noticed a increase in hp and tourque but all I got was an increase in noise. I just couldn't afford a $500 dollar tune at the time. Your truck might be a little better off cause your only deleting the cats and not adding headers but you will certainly have a check engine light on after about 50 miles without a tune. Also is this your daily driver? And how strict are the state emission stations during inspection? If they put the emissions sniffer on your exhaust your will surely not pass. If anything buy a set of headers that come with a y pipe and no cats and keep your stock exhaust around in case something goes wrong. Once you hollow out you stock cats you will not be able to go back and a new set cost about $400 or more depending on the brand.
    Best of Luck to ya.
    06 Silverado Reg Cab Stock except for flowmaster 40 muffler, and monroe sensatracs

  3. #3


    Unless you have some major head work, healthy camshaft etc.. you won't see a performance differance over the stock cats. The new cats flow very well as compared to the early cats. Keep them on your truck will run better.

    2005 Chevy Silverado Z71 Crew Cab
    6" Skyjacker lift w/Edlebrock dual front remote resoviour shocks, single rear remote. Rancho skid-plate.
    17" x 9" M/T Classic Lock Wheels, 35" BFG A/T or M/T tires
    4.10 PercisionGears w/factory locker, T/A Performance rear-end cover
    Banks CAI intake, ported throttlebody, JBA coated headers, over-sized Magnaflow cats, Magnaflow cat back exhaust, Diablo tuned
    B&M aluminum deep transmission pan
    Warn brush guard w/Warn 9.5 XP winch, PIAA bulbs, Line-X bedliner, AWS Black tool chest, Extang tonneau cover
    Weather Tech floor mats
    Cover-Craft seat covers
    Dash mat cover
    Formula One window tint
    One black Lab in rear seat.

  4. #4


    Good to know thanks guys

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