Mine ran great and had no engine codes, but it wouldn't pass emissions on a dyno. Monitoring the voltage on the O2 sensor proved that it was reacting very slowly and not running properly. Now I say it ran great. After I shortened the flange to emulate the stock cast header position of the sensor, it absolutely smokes. You wouldn't know it is the same car. The exhaust fumes don't stink any more, there is more power everywhere, but especially in the top end, and driveability is remarkably improved. It goes on the dyno this morning, so if it passes emissions, it will prove what I am saying. The difference in performance is worth taking the headers off and doing the modification. Thorly's tech support agreed that it probably didn't work correctly. Remember, back when these were OEM, they only had a very basic exhaust analyzer, and it most likely passed that just fine. The dyno is another thing all together. I'll let you know how it comes out.