1997 f150 4.6

OK so I have shorty headers on the truck right now to start with then 2.5 inch to the cat then 3" from the cat back. I hear a rattle sound when Im under the truck and pretty sure the cat or cats are pooched. Im getting horrible fuel mileage and the check engine light is on. Code came up as drivers side o2 sensor. I am not sure what those contraptions are in the down pipe after the header. They are triangle shaped. Are they resonators, pre cats or another cat? I was hoping to buy 2 new high flow cats and install them into 3" down pipe from the headers then back into a single pipe. Will my truck run any worse? will the check engine light come on if I remove those triangle shaped parts? Sorry guys for my wording I am just not sure what they are. I dont have tons of money so I usually do everything myself so I looking for the easiest route from the headers to the Y pipe as I will keep my 3" setups that is after the y pipe. I have a gross sounding exhaust leak somewhere too but Im thinking its the headers. I can only hear it when I ham on the throttle. Im looking for people that have first hand experience with installing aftermarket exhaust and want to know if those triangle shaped parts cant be removed entirely. Thanks guys.

 

sorry guys. . . . . . . Search function. I now know they are pre cats but am getting some mixed feelings. Can I leave the pre cats and remove the big cats or will it run worse? I dont want a check engine light. I want better fuel mileage and I really believe that the main cats are cooked. The truck is insanely loud though .

 

I would suggest 2 Magnaflow high flow cats to replace those 4 stock cats. If you order the ones where the rear O2 sensors get screwed into the cats you won't get any codes. Cutting out your smaller pre cats and replacing them with a straight piece of pipe is fine too and it seems a lot of people are doing it. Or you can do what i did and delete all four cats and replace with a straight piece of pipe and use the gotts O2 mod on the rear O2 sensors.

Also this should be moved to the exhaust section

 

when I got my exhaust run I had the shop cut out the 4 stock cats and replace with a high flow on each side. they welded in some o2 bungs and reinstalled the o2 sensors. no cel or any other problems thus far.


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same here... i got 2 magnaflow highflows and gutted 2 of my original cats (emissions test). i played hell getting everything right to pass emissions though. ended up having to mod some o2 sensors and other things.

 

Definately replace the cats with two magnaflow high flow cats. The difference in volume from your exhaust is amazing. It's simply impossible to make it loud with the stock cats. When I replaced mine two years ago the stock ones (scrap yard) paid completely for the two high lows

 

Oh and of you choose the high flows and straight pipes after make sure everything else on your truck is legal. It will draw unwanted attention sometimes

 

^ exactly
Side note how much you get for your cats i only got $115 about three years ago?