Car is running, but exhaust sounds bad around 2200rpm

[Wi Stang]

Well I just got my car running the other day after putting in the Trick Flow h/c/i and a vortech sc. I'm pretty impressed with it so far. It idles pretty good, and it really moves out compared to before. I haven't gone WOT on it yet until I can get it to the dyno. But I noticed that when I hit around 2200 rpm to about 2500 rpm it sounds like the ehaust is rattling really loud or something. Above and below that rpm range it sounds good. It didn't do it before the swap, but I heard it the first time I drove it after. I checked all the clamps, and clearance around it but everthing looks OK. Is it possible something in the muffler loosened up and is rattling at only that specific rpm? I'm out of ideals on what it could be. Any suggestions would be appreciated.
The exhaust system consists of BBK unequal lenght headers, Bassani off road x, Flowmaster 2 chambers.

 

[Wi Stang]

Well I had a friend of mine listen while I reved it up to the range where it rattles. He said it sounds like it is coming from the mufflers. Is there something in the Flowmaster 2 chamber that can break free and cause that noise? A baffle or something? The noise is pretty annoying.