interesting noise...
 

A friend of mine needed to send his car back to the dealer for a new motor, but needed a cat (he bought his with a mid pipe) so I sold him mine and traded it out for the mid pipe. Of course now that I put it on I have the cel P2096 Post catalyst fuel trim system too lean (Bank 1).

I am sure this was caused by the secondary o2 being confused as hell, which is to be expected. However, I have developed a noise that can only be heard between 2500 and 3000 rpm. I found this video on youtube of a FD making the same noise (mine is a 05 8 w/ 70k miles)
http://www.youtube.com/user/blind26#p/u/3/gq1T2_gz6tY

in the video, the sound I am referring to is at :08, :10, and ;13 seconds (not referring to duration, but markers in the video) The poster of the video said he was having an issue with "lean pop". is this what I am hearing? if so what can I do to correct it, minus putting a cat back on? The only mods on the car are the test pipe and vfad removal. any help would be great.

The only thing you can do is get an AP. There is 10 days left before they are discontinued.

The other option is to remove the midpipe.