So the other day i was sitting at the stop light with my radio off and my windows down and I start to here this weird crackling noise coming out from underneath my car on the passenger side right where the cat is. Im not sure if this is normal im guessing not but I dont know what it is. Im asuming its something to do with the cat.

 

It is the eshaust pipes expanding & contracting, no big deal.

 

Oh ok thanks pete