The original owner put this on my S to eliminate the need to plug in a o2 sensor to the test pipe. It appears to work since I had no secondary o2 sensor and no CEL. I pulled it off as I put the stock cat back in.

I want to sell it but I have no idea what it's worth. Google has no answers either. Perhaps someone knows?

 

Not much in my opinion, you can purchase a regular CEL delete for $15 or less, so there's no need for anyone to spend more than that on something that does the same thing.