I have the ebay headers for my m coupe. JVT headers. Fit is good and I orginally left the post cat (rear) o2 sensors out. I just unplugged them under the valve cover and took the sensors and pluged up the post cat o2 sensor bungs. This caused a Service Engine Soon light to come on. This has no effect on performance as the post cat o2 sensors are only used because of obd2 diagnostics for the cats.
The light was kind of annoying so I took out the headers and welded up 2 more bungs on them in my garage as so they would clear the transmission. And used the "spark plug fouler" trick to space the o2 sensors. Then used my OBD2 tool and cleared the codes. No light came on but after a day the light came back on with a post cat o2 code reading lean, probably because they were spaced too far out of the exhaust stream. I guess the ecu is really picky about the post cat o2 signals. Next i might try a o2 simulator or the forsure method and remove the ses light bulb in the cluster.
I have a post floating around with more detail but no pics.
As for performance gains I have no actual numbers but you can ask chaforjohn, he's driven mine then his back to back, and the response and power on the jvt headers do make a difference.
Hope this helps.
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Originally Posted by jmenge
I would like to order the ebay headers for my z4 M. I wish someone could describe or show a picture of how the rear o2 sensors need modification to clear the transmission. Let us know how your install goes and best of luck!
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