Recently purchased an 89 740 w/ 112,000 miles. Car runs and looks good. Car had exhaust leak at cat. inlet. Fixed that sounds much better at idle. The exhuasr is still way to loud between 45 and 70 sounds like a roaring kind of noise. Most of the time the noise will stop when you let off the gas, but now sometimes it sounds like it is sucking something in when you let off. The rear muffler does not look to be original and has not markings on the underside. Anyone have any ideas???