Does faac.flt work in AA 2?
I put it and the DLL file into AA2's root folder but don't see any AAC/M4A formats available in Open or Save.
I don't recall it working. I think it needs to be recompiled with the new Audition SDK, and I don't know of that being done yet (it's not an open source filter AFAIAA, so the original author would have to do this). Also, I tried to create an MP4 audio file by exporting via that filter, and the resulting file wasn't readable in other MP4-aware players.
So, I tend to do my format conversions in Foobar2000 these days, then just load wav files into Audition. I still believe an AAC/MP4 filter should bundled with AA.