Longtube Headers will always throw an oxygen sensor code unless they are tuned out.
There's really not a problem, it's just reading oxygen levels outside the factory allowable limits because you're flowing a lot more air than factory.
If you don't want to touch the tune, your cheapest alternative is to purchase a Bluetooth OBDII scanner, plug it into your car, and download the Torque app and clear the CEL every time it pops up.
That's what I do and it works like a champ
