exhaust leak?

Started my car on one cold morning and went back inside to shower. Came out to leave to find exhaust steam coming out of my left rear fender well... I'm almsot positive that that is not a good thing. I plugged the exhaust and the quantity of steam doubled that was exiting around the wheel. Does anyone know where i can purchase an aftermarket oem system from my manifolds back (including cats)? I've also got obnoxious rattling that isnt pinging cause I run mid grade in my truck... Any input at all is greatly appreciated...

took it apart to find a muffler full of pin holes and the pipe was rusted in half..