Could I remove the cats on my 99 4.6 s-cab and run true dual straights with factory size pipe and not have.engine problems

 

yes, you will get a check engine light for the secondary o2 sensors, unless you trick them (search the forum for it), i am about to do the same to my 99 xlt....

 

You'll probably want some kind of glass pack or muffler on there becaus my friend straight piped his Vortec and it runs like crap and sounds bad too. These fuel injected engines need a little back pressure on em.
And I cut all my cats off and have a check engine light on. I had them clear it but it came right back on. I'll post a video off my set up if you want to hear it.

 

Please read. Thanks
https://www.f150forum.com/f11/exhaus...re-myth-78102/


OP: Any time you alter the cats, it should be properly done and then accounted for in tuning. When the flow past the front O2 sensors is altered, a/f ratios can get out of line. You can delete the rear cats and do the Gotts O2 sensor mod. This will give a high volume of sound and stay legal. You could also do high flow cats. Running completely cat less is federally illegal for an on road application that originally came with them. The rest of your system beyond that should include a crossover (X or H) and ~2.5" pipe.

 

So it doesn't need back pressure???

 

Nope. No motor NEEDS any sort of pressure forcing gases back towards the cylinder, getting the gases away correctly for the application is where differences are. Welcome out of the stone age myth land of backpressure and to the new age of enlightenment.

 

i wouldnt remove all four cat and have straight pipes with no muffler my brother took his do that that and they didnt put a muffler when he hit the gas you couldnt hear yourslef think a cop gave him a warning and told him to go back like you could hear it 2 miles away lol so he got muffler put on and it sounds good

 

Oh ok thanks lol I just always assumed it was supposed to have it for the computer.


But he'll still want some kind of muffler or glass pack because they can be obnoxiously loud straight piped.