First just go ahead and get the Wester's updates are free, if you have a 2007 he has an ECM he can swap with you (it's my spare). I don't think pulling the stock cat is a very good idea on a stock set up, but from my experiance it seems to go richer not leaner, that is just perception not fact. I wish it would stop freaking raining so I can test this tune.
As far as louder, not much really sounds better to me but not a lot louder, I think it gets louder when you get in it but can't really tell yet. It is a lot quieter that a Street Race with the stock cat, no highway drone, I can still hear the stereo.
It seems as best I can tell to spool up faster, I just keep spinning the tires cause of the wet roads, more so than before with the cat so I have to say it does increase performance.