Yes Federal Emissions are covered by a longer warrenty than most cars warrenty. But it is not transferable. Original owner only.

 

Still have not solved this issue. No additional codes and there are no exhaust leaks. I double checked connections and manifolds all the way up to the heads with a mirror. Exhaust manifold bolts nice and tight. No leaks, no cracks. The cat welds are clean and solid. Guess the only thing left to do is change out the O2 sensors? That's a $450 dollar gamble I'd rather not take, but I suppose at my mileage it's getting to be about that time anyway.

It will only throw the code when I'm climbing a grade or accelerating on the highway. Don't know what to do about this. This monkey has been on my back for way too long. Should I attempt to replace just the one O2 sensor behind the cat?

 

You don't have 02 fault codes, and yes they could be causing it. You should have gone back to the supplier and asked them what to do when it started, now you are out of luck.
If you have a good scanner that can snap shot the signals from your 02's, I would check them first and then get back to us.