tail pipes & wiring harness 91 chevy
 

My car was breathing lovely then my oil got low but not bone dry. every since then the tail pipes(dual) sound a little louder and rougher than before and a noise i cant explain souns like a putting sound or someone shaking a bottle with little beads in it.

Also the person who changed my engine out broke and lost the cord that comes from the wire harness to the ac compressor any suggestion on how to fix it and could i just replace the whole harness and how hard would it be.