Hi, I wanted to create a new rendering profile and have it not change the current MP3 audio bit rate when rendering.

Here is how I came to the profile page...
Click Render > M-PEG4 > M-PEG4 25000k > Create new profile

The arguments to change...
f=mp4 acodec=libmp3lame ab=128k ar=44100 vcodec=mpeg4 minrate=0 b=25000k aspect=%dar mbd=2 trellis=1 mv4=1

So this part...
ab=128k

Would I edit it like ab=0 or ab= or maybe even something else so the bitrate wouldn't change?

Thanks.

Uh, figure out what the source bitrate is, and set ab to that? There is no way to express "use the same" because when you can have multiple tracks and clips of various format the question would be "same as what?" Think about it.