Nothing wrong with the O2 sensors, that means they are working.

was it burning oil and coolant?

You need a new cat, Try eBay less than $200.

 

X2 not the O2 sensors, a cooked catalytic converter.

 

 

Why did you change engines?

Only 1 cat on a 2006, why did you replace it?

 

 

 

Well, rods don't usually get thrown when the sump is full of oil. I am guessing a lot of oil got burned in a short time. That kills catalytic converters.

Catalytic converters don't make noise when they fail, they throw p0420 codes.

It is not unusual for replacement cats to be of inferior quality.

 

 

You can replace the entire down pipe assembly with cat for under $200 off ebay. Very easy swap.