I cut my muffler off when i added high flow cats. It's FREGGIN loud and I LOVE IT!!!! My neighbors probably hate me but it worth it.

i did this to my 07. had the muffler cut off and just a piece of new pipe welded in its place. love the sound but when you get on the pedal ive been told it sounds like a trophy truck haha. on cold starts in the morning it is very loud!!! it gets quiet after about 30 seconds but damn right when you start it its friggin loud!

Nothing to be concerned about other than determining the correct series of Flowmaster muffler to meet your desired level of sound. Feel free to PM me if you have any specific questions.

I did this to mine and ended up keeping the cats on to but me and a buddy just put a single inlet dual outlet and we made a dual exhaust from there but you can easily do what the others said and just run a 90 or 45 degree with an extension in need be so that the pipe doesnt lead right under the truck, trust me the fumes will make you drowsy after a few minutes and give you a serious headache. But the sound of it is pretty loud when you hammer down on the throttle but its almost invisible when your cruising even at highway speeds.You can hear it but its not where you hate driving it daily. Also it will cause some of the low end torque to fade. when i cut my gibson dual side exit exhaust out it wasn't breaking traction as easy but i love it. it holds gears alot better and firmer, its not causing it to downshift early anymore.

My truck is an 04 with the 5.4 an I cut out the back 2 cats and also replaced the stock muffler with a flowmaster 70 series. And I LOVE the sound!! Has a nice rumble at idle and slow driving but at highway speeds it's not much louder then stock

So from what I am reading here, you guys got rid of the catalytic converter completely? Or did you add a straight pipe after the cats?

Well my truck had 4 cats and the front 2 were the ones with 02 sensors so I left them alone. But I cut out the 2 back ones as they didn't have any sensors. Then I all new pipe put in from my the cats to where I now have a flowmaster 70 series and reused my stock over axle/tailpipe. My reason for the was tht particular section of pipe wasn't in good shape any more. However I had an exhaust shop do all this for around $300 out the door

I have a 2008 Ford F150 FX4 SuperCrew 5.4L V8. So you basically straight piped from the rear of the front two catalytic converters, then installed Flowmaster in place of the other two catalytic converters in the rear?

I hope those of you that cut off the cats kept them. When it comes time to sell or trade in that truck, the cats will have to be re-installed. Its a federal law (supersedes any lack of state inspections or laws) that states all smog/pollution equipment must be intact to sell a vehicle.

Even with an "as is" clause in a bill of sale, a buyer can come back and nail you for the cost of cats install. A dealer cannot re-sell a vehicle that has had this equipment removed; they will have to re-install it before they can legally sell it.

My son was served papers two weeks after selling his Subaru WRX STI with its removed cats. The buyer went to register it in their state, and it failed the visual test; the buyer contacted their lawyer, and my son had two options: refund the purchase price (and get the car back), or pay for the parts and the equipment installed. He refunded the price, and took the car back, as he regretted selling it anyhow. He still has it today.

Just a heads up.

Thts correct but the flowmaster went in place of the stock muffler