Last year I purchased a Bushmaster 16" A3. I love the gun to death. I have the 16" barrel without a compensator or flash supressor. The rifle is VERY loud and has a massive flash signature. (on the range they call my rifle a flame thrower) I have considered the AK or Ycomp muzzle breaks. Will a muzzle break reduce either the noise or flash? Will adding a muzzle break affect accuracy at all?  

I'd say go with a Wilson Combat tac brake. It isn't as loud as some other brakes I've tried(AK, Smith Ent, JP) works great at reducing flash and stabilizes the muzzle for faster splits. As an added bonus, it's cheaper than most of the competition. It also looks somewhat like an A2 FS.  What a deal!

By adding a muzzle brake, you will increase the noise.  People shooting to either side of you will especially notice the increase in noise.  As far as flash, a muzzle brake isn't designed to reduce flash signature, but in some cases it will.  Also try experimenting with different brands of ammo to try to reduce the flash.  Accuracy probably won't change significantly, but you should notice that the brake will help stabilize the muzzle during rapid fire.

Forgot to mention in the previous post, I haven't noticed any difference in accuracy between braked carbines and guns with A2 FS or plain muzzles.

If you think your rifle is VERY loud and has a massive muzzle flash just wait 'till you put on a brake/compensator. What you really want is a pre-ban with a flash-supressor...