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  1. #1

    Default Aftermarket exhaust and AFM question ...

    I have a buddy that just bought a 2011 Sierra 1500 Crew-Cab with a 5.3.

    He had a 2008 Silverado reg-cab short bed 4.8 truck that he put a Flowmaster cat-back exhaust system on (one muffler, dual exhaust outlets) and it sounded really good.

    He wants to modify the exhaust for better sound on this new truck, also ... however, this new truck has the Active Fuel Management (AFM) system ... has anyone done a Flowmaster or equivalent system (either single exit or dual) and maintained the AFM system?

    I have a new Camaro SS, and all the guys on the Camaro5 forum (both V8 and V6 owners) have complained about the horrible drone from an aftermarket system when the AFM is maintained ... wondering if the trucks have the same problem.

    Of course a programmer can disarm the AFM (like I did on my Camaro), but that is an added cost and figuring will probably hurt the mileage ...

    Any shared first hand experiences are welcomed and appreciated ...

  2. #2


    I have AFM enabled with dual exhaust, and besides the exhaust getting quieter i dont notice anything odd. Though i have heard some people complain about it on some other mufflers.

    Using DI/DO 14" Magnaflow.

    2009 Silverado 1500
    5.3L / 3.73 G80 / 4spd / 4x4 / LWB/ Ext Cab / HD Tow-Haul
    2.25in ReadyLift Level Kit / 3in blocks/ 3500lb HellWig / 265x65x17 Wrangler AT
    K&N Filter / AirRaid MIT / MagnaFlow 2.25" Dual Exhaust / HyperTech MaxEnergy

  3. #3


    I have a buddy with a '10 5.3 running the Gibson supertruck cat back and when he hits 4cyl mode it sounds like a tractor. Another buddy has a '11 5.3 and put in a Flowmaster 10 series 1 in 2 out and sounds amazing by the way, but sounds way better in 4cyl mode than the Gibson. Hope that helps....

    ________2013 4C Rated__________

  4. #4


    Yeah I've heard a lot of people talk about this problem. I purchased a Flowmaster Super 40 that I'll have installed when I get back home but I'm also picking up a SuperChips programmer so that I can turn the AFM off. I don't mind it now with stock exhaust but I don't want to deal with the drone. I really wish GM would have installed a switch that you could use to turn the AFM on and off. I didn't buy a fullsize truck to run on V4!
    2010 Silverado LT Z71
    3"/2" Leveling Kit (will install after Deployment)
    SuperChips programmer

    Flowmaster Super 40 with turn downs
    Looking for the tires now!

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