Editor's note: The following is an analysis of what I consider to be a serious design flaw in the Courtesy B-Pipe. Courtesy designed their pipe to be a universal fit both for Maximas with and without an O2 sensor behind the catalytic converter. Unfortunately, for cars which do not have the O2 sensor, the Courtesy design is a poor compromise since its installation requires that a restrictive Nissan-made OEM extension piece (which is not on the car to begin with) be added between the B-Pipe and the catalytic converter. The extension piece is only required to house the O2 sensor, and on cars which do not require it the sensor hole needs to be plugged and this extension piece inserted between the cat and the Courtesy pipe simply to make everything fit!
What Courtesy needs to do is design a longer single-piece version of their B-Pipe which fits 95-99 Maximas without the O2 sensor behind the cat. Other than this one design flaw, the Courtesy B-Pipe is an outstanding piece of work.