40359 Borla Muffler install

Sidewayz · October 30, 2016

Flapper is open. Heading for a 30 - 45 minute road test. Idle sounds awesome. Stay tuned for an update.

Rawyzf · October 30, 2016

Flapper is open. Heading for a 30 - 45 minute road test. Idle sounds awesome. Stay tuned for an update.

Good to hear it! Remember too, it takes a couple weeks to break in the muffler.

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Sierra Jon · October 30, 2016

Will keeping the flapper open give it more sound??

A surprising amount more actually. Mostly at start up and idle. WOT isn't much different because theoretically at that point the valve would be open due to exhaust flow.

Best 2 minutes spent on these trucks.

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Sidewayz · October 30, 2016

Big difference. Seems to get a bit louder as I'm driving and the muffler is burning in. I added an AEM air filter with the MIT also.

djxn40 · October 30, 2016

So I finally just had the muffler welded in. Kept the flapper valve and resonator. Not impressed with the sound. Will removing the resonator give me a much louder sound or will it be obnoxious? Looking for info from anyone running the same combination.

Thank you in advance

That sucks I went with the muffler and flapper delete. Kept resonator and I'm extremely impressed... sounds awesome . Of course I got rid of the dreaded v4 and raised my mpg

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Rawyzf · October 30, 2016

Big difference. Seems to get a bit loader as I'm driving and the muffler is burning in. I added an AEM air filter with the MIT also.

Best part of the MIT is that you can finally see the engine and reach in there.

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Sidewayz · October 30, 2016

Drove another 45 minutes home and wow it sounds much better and the truck has some more pep it seems also. Or my foot is extending the pedal lower faster..lol

cbrsilv15 · October 31, 2016

Told ya. Flapper was a night and day difference for me with my Borla.

Sidewayz · October 31, 2016

I think taking the resonator off will be too loud. Now considering a handheld tuner.....

juscuzram · August 24, 2017

That sucks I went with the muffler and flapper delete. Kept resonator and I'm extremely impressed... sounds awesome . Of course I got rid of the dreaded v4 and raised my mpg

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I know I'm resurrecting an old thread, but you're saying your MPG went up with the AFM turned off? I love that Borla sound, but I also love the MPG that I'm getting haha

Nasty · August 25, 2017

I know I'm resurrecting an old thread, but you're saying your MPG went up with the AFM turned off? I love that Borla sound, but I also love the MPG that I'm getting haha

In a way mine did. With afm on I'd fluctuate between 25-30. With my afm o I stay at a constant 26ish.

juscuzram · August 25, 2017

In a way mine did. With afm on I'd fluctuate between 25-30. With my afm o I stay at a constant 26ish.

Interesting. I'm getting about 18 in town and 21 - 22 on the highway right now. Calculated by Fuelly app. I clamped my flapper open the other day, and so far it looks like I may have picked up an MPG.

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Nasty · August 25, 2017

I also have a lowered regular cab. And smaller tires made a difference

juscuzram · August 25, 2017

I also have a lowered regular cab. And smaller tires made a difference

Yeah that's defnitely a little lighter and more aerodynamic than my CC. I'm planning on leveling the rear, so maybe that'll help some. I filled up for the first time since clamping my flapper open and I went up almost 2 MPG city! I'll see if it keeps it up, but it's crazy that just that little bit of restriction makes that much difference.