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  1. #1

    Default Aftermarket High Flow Cats vs OE Cats... same performance HUh?

    I inquired today about high flow cats for my truck today and the first shop wanted $300 installed for Magnaflow I believe...

    Then I called a shop recommended to me by a co-worker -

    I asked what they run and he said " I wouldnt take your money." Then explained that the stock cats are just as efficient as the aftermarket.

    So it looks like I have $300 bucks to put else where huh?

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  2. #2

    Enkeiavalanche's Avatar
    Join Date
    Apr 2010
    Piermont,NY, back in Northern NJ now, But may be in IL soon....


    I have heard the same thing over and over.. Save your money unless they are clogged.. The factory ones are 3 in and very open..
    08 Z71 Avalanche Mods to date: K&N CAI,Hellwig Swaybars and End Links, Corsa Sport Exhaust, Superchips Programer,IPCW LOF & 3rd brake light and tails, AMI Gas door,Show Hooks and Door locks, Enkei Wheels, with Pirelli tires, StreetScene Bowties, Grant Steering wheel,Muth signal mirrors,SSBC Big Brake kit,Huskyliner Mug gards,Floor mats and Hood shield, McGard Lug nuts and locks, Bedrug, Cervini's Ram Air hood,35watt HID Fog lights, Sylvania bulbs all around ZXE's Highs and Lows, WhiteNight Back up lights,Sirius and HD Radio, SnugTop sitting on deck now Got a Softopper on now,Tempress Boat Hatches.... New Bilstein shocks are on... New Mods coming soon..... X

  3. #3
    Sr. Engineer IPFK83's Avatar
    Join Date
    Jan 2011
    Jacksonville, North Carolina, United States


    I have also been told this too but I bought mine anyways b/c I had to redo the entire exhaust system so I figured why not.

    2006 1500 4x4 extended cab short bed
    SAS 12" suspension lift
    38x15.50 Mickey Thompson ATZ
    20x10 Mickey Thompson Classic II
    FOA custom shocks
    Dana 44HD front axle
    14 Bolt SF w/ detroit locker
    yukon 5.13 gears
    Dynatech Long tube headers
    Dynatech y pipe w/ high flow cats
    Magnaflow muffler
    Tom woods custom dual cv rear driveshaft
    K&N AIRAID system
    Hypertech power programmer
    And much more...........

  4. #4


    Quote Originally Posted by Enkeiavalanche View Post
    I have heard the same thing over and over.. Save your money unless they are clogged.. The factory ones are 3 in and very open..
    One less mod to worry about I guess

  5. #5


    The factory cats are highflow. I went with 1/4" larger diameter cats and "Y" pipe. It made a differance. It complimented the headers and cat-back.

  6. #6
    Master Mechanic clgoch187's Avatar
    Join Date
    Aug 2010
    Gettysburg, Pennsylvania, United States


    stock cats ARE high flow cats..... as long as they are in good condition there is no reason to replace them.
    03 Silverado 1500
    285/75/16 BFG's
    2 Blaupunkt 10" vW1000 subs in Subthump box
    ProComp Level Lift & 3" rear blocks

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