I actually bought one new just to see it and compare it to my ATP DP and it is about as close to an exact copy as you can get. The welds are well done and the materials appear to be identical to the ATP, except the ebay DP is polished, BUT it isn't available with a high flow cat. I installed it to check for fitment and function. Perfect fit and function. I "almost" would never recommend an ebay copy of anything, but in this case I have it and recommend it. You could buy ~4 of them and still be ahead of the price of ONE ATP DP. Don't get me wrong, the ATP is a great DP. I bought a catted version new many moons ago and it has performed as expected. I still have my catted ATP DP as well, NOT for sale.
You will need some method to eliminate the CEL for low cat efficiency, but no problem if you have the latest version of ATR. You can turn off this CEL logic in the ECU. No CEL or code.