2002 a4 3.0
 

Hey, recently ive noticed a slight rattling upon acceleration/slight revving engine in nuetral. The other day my CEL came on. Today i was a little late, doing abt 95 on highway. Later i went in a store left car running, noticed my cars now running louder. So i know it has something to do with exhaust. Can anyone help with the info ive given. What the issue could be, and what parts. Also any reccomended websites to order at a good price.

Also. What would be expected cose of labor?

Its on the left side also. I listened to the side n the exhausts