From Borla exhaust back to OEM?

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Nov 23, 2014
I recently purchased a 96 with a completely documented top end rebuild for a hell of a deal. During the rebuild, the PO installed a Borla header. Something just doesn't look right. Does aftermarket exhaust normally run this close to the fender well? I have a few O2 related codes,p141, p135, p125 so I decided to investigate further. I have what looks like O2 block off plates and some patch job in front the cat. I see no O2 sensors at all. Not even pigtails. Granted its freezing out so I didn't get deep into the truck yet. What do you experts think of this? I'm tempted to just revert back to all OEM this spring.





You sure it's a borla catback and not just a muffler?

The mandrel bend all their stuff to my knowledge and use a high quality t304 stainless. Which shouldn't look like that
I'm not sure. I have the receipt for the header and the muffler is borla as well. Receipt for the header also states "custom" Y pipe. So the PO kept the stock cat to save some money I guess.
After better inspection, it looks like the PO decided to delete the upstream O2 by grinding the bung off and using hose clamps to keep the patch on. So I need to replace the y-pipe. Do you need the cat itself for the engine to run smooth or can I just go cat less with new O2 sensors? We don't have vehicle emission testing in my state.
There's a handful of recent exhaust threads on here. Search "Magnaflow y-pipe" and that should hit my thread and at least a couple others.
There's a handful of recent exhaust threads on here. Search "Magnaflow y-pipe" and that should hit my thread and at least a couple others.

Thanks for the help. Im an idiot when it comes to searching

To clarify, I DO need at least one cat in order to run properly with no CEL?
Got it. Thanks
You could try installing the post cat O2 sensor in a "plug defouler", which is just a spacer that pulls the sensor out of the exhaust flow, and can prevent CEL's from the absence of a cat, but as stated, why bother.
THANK YOU to all of you who helped me here. This forum is a great resource!

Heres the deal, The PO installed a DOWNEY OFFROAD header, "custom" y-pipe (poor design), Stock cat (both O2 sensors missing, plugs zip tied up), Borla cat-back.

My question is will any y-pipe w/cat (walker, magna flow) bolt up to the Downey headers?

No result when searching, just one thread about Header choice.

Once again, sorry for the confusion. Im not trying to delete the cats, just want everything operational and CEL gone.
I would expect any Y-pipe (stock or aftermarket) should bolt up to the Downey headers, otherwise you'd require a whole new exhaust anytime you installed that header.
I too would expect that OEM and most aftermarket y-pipes to fit behind the Downey header. Magnaflow seems to have worked for lots of folks.

Several threads over that last few months that detail other members trials and tribulations repairing and replacing worn out exhaust components.

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