Alright.
So I go out and start my truck, and each morning I swear the exhaust gets louder and louder. In fact, I have went from a low rumble in the cab to a loud drone that vibrates the little plastic piece behind my seat. Also, this past week and a half, I have noticed a shaking in the cab as if the engine were slightly rocking side to side. You know that side to side motion it gives when you first start up, well it doesn't stop in my truck till I am going for a while. And to add to all this, when going up the interstate at around 75, I noticed that when I speed up to 80 or so the power just leaves. It's like it won't give me any more power after 75 unless I stomp it. So what do you think could be causing this?
Could it be an exhaust leak I'm not noticing?
I looked under the truck and inspected the piping, but all I noticed was some black carbon build up around the connection of the y-pipe to the inlet of the muffler.

Here's a pic of the y-pipe connection: