My uncle recently gave me his 325is. I needed to swap the policy and ownership. In order for me to do that, i needed a smog check. I went to get a smog/emissions check and i failed! :cry It read 1300 at 15mph in the NOX reading :wtf. That is almost twice the passing limit (about 700). Why could be causing this problem. The O2 sensor has been replaced. The only thing i can think of is the cat. If it is the cat, can i go to the muffler shop and tell them to weld on a universal cat? one more question will high flow cats pass smog?