Exhaust sounds messed up, any ideas?

So the other day i took my car out, after driving it for a little while i noticed it sounded completely different then it did before. Its gotten way raspier and way louder and sounds kind of terrible. Ive got Pace Setter LT's, and a off road y pipe and a LM1 exhaust. There is a small amount of air leaking out right before the muffler but im pretty sure its always been like that. Its not welded on but i checked all the clamps and they are all tight. Anyone have any ideas?

I would change the lm1 muffler out. I used this http://store.summitracing.com/partdetail.asp?autofilter=1&part=MOR%2D94051&N=700+400105+4294923429+4294922711+115&autoview=sku
They also have it in stainless.