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Flowmaster cat back or muffler

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New to the forum here, I just installed a rough country 3.5" lift on my 2013 Silverado and I am looking for ideas on a more aggressive exhaust note, so far I have narrowed it down to Flowmaster 40 or 50 series. Has anyone had trouble with engine codes or cat issues after installing an aftermarket muffler on a 5.3? I had a F-150 with the 5.4 that was plagued with cat problems after a install (it was probably not the muffler that caused the problem...and cue the ford Chevy jokes). Just looking for some advice from Veteran Chevy owners.



From a newbie

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I had everything from the muffler on back on mine removed and had a Flowmaster Super 44 single in/dual out muffler put in. As long as you don't touchthe front 2 cats then you won't get any codes. The 3rd cat isn't monitored and GM decided to just make all of the new trucks Cali legal so that's why that 3rd cat is there. My truck is loud and very aggressive, the Super 40 is about as loud I believe, just isn't as aggressive than the 44. The 50 I don't know. If a V4 mode drone that sounds like an 18 wheeler's engine brake will bother you then you'll need the flapper valve that's in the stock system or just have AFM turned off. I had Flowmaster Super 40s on my old 98 and also no problem other than 1 cat went bad the whole time of owning that truck ('04-'14) and that had nothing to do with the mufflers of course.


I've never been a fan of a cat-back exhaust because of the cost. Sure you'll usually get mandrel bent pipes, but you really won't feel a difference unless it's a performance car.

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Thanks for the input guys, I'm not really looking for performance just a more aggressive sound. I was just worried about effecting the emissions because when my F150 cat went out at 30000 miles they wouldn't honor the warranty because of the aftermarket muffler. Fool me once....


It is always good to keep the stock exhaust and put it back on when warranty work is done.




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I cut the stock muffler out of my 2011/5.3 and installed a Flowmaster 50. A little rumble to let know its not stock. Put your foot into it and it wakes up nicely! NO cab drone at all unless pulling a heavy load, then you will notice it more but that is the territory expected.. You may want to get rid of the AFM so you don't hear when the V4/V8 switches.. Good luck!

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