Hi, i hope some one can help. I have had a Cup a few weeks now but i have a rattle that seems to be coming from the middle or rear of the car. The noise only ever comes between 5000-7000rpm. I have had the middle section of the exhaust changed under warrentie but the noise is still there. It sounds a lot like engine pinking but is coming from the exhuast area. Could it be a heat shield or the cat?? PLEASE HELP!!