I have been on the .org for sometime now and i cant remember if anybody has posted a dyno chart of the gains they reseved from a catback exhaust. i have just seen header and y-pipe dynos charts.

 

I did one a while ago. Have someone search for "OBX+Dyno" and it should come up with the results I posted. You can see the rough results at:
http://www.nissanx.net/gall/albun08

I did an indepth analysis of the data from the dyno in one of the threads that you should be able to find using those search keywords above. Just look for my username as the starter of the thread

 

Here's 2 threads that provide some info. One by bgates and the other by emax. Save them so you could post them for the next guy who asks this question.

http://forums.maxima.org/showthread....highlight=dyno

http://forums.maxima.org/showthread....altima+headers