Originally Posted by semtex

Well, I'll share my own past experience and allow you all to draw your own conclusions. On my 350, I ran a set of Kinetix resonated test pipes. They did not have the extended O2 port, and they'd throw CELs every 200 miles or so. The remedy was what's known as the 'non-fouler' or 'anti-fouler' method, where you take two anti-foulers and drill one out so that the other one fits into it. What you do is screw one end into the O2 sensor port, and then screw the O2 sensor into the other anti-fouler. Now, the anti-fouler you're screwing the O2 sensor is not the one directly connected the port. You're screwing the O2 sensor into an anti-fouler that is screwed into another anti-fouler, which is screwed into the port. The anti-fouler that you're connecting into, then, is 'nested' into the other anti-fouler, so it's protected from the actual exhaust gasses. Net result -- no more CELs. By welding an extended O2 sensor port right onto the HFCs, Berk is trying to make our lives easier by replicating this anti-fouler method without us having to manually go buy the anti-foulers, drill one out, etc. Now, I'm not 100% sure on this, but I think they may be missing the 'nesting' part of it. In other words, the O2 sensors are being situated back away from the direct line of exhaust gas, but I can't remember if the end of that extended port is actually blocked off or not. If it isn't, then gasses aren't actually being completely blocked off from the O2 sensors. So that would explain why some people are still seeing CELs. If it is blocked off, then it's properly replicating the non-fouler method.

Here's a DIY link to the non-fouler method:

Stop CEL With Test Pipes - Nissan 350Z & 370Z Wiki