Good Morning, I am new here and have a question about a 2007 Jetta. At idle the car appears to sound fine no misses, and when you rev it, it sounds normal, but when you get to 20MPH and above it starts to sound like and exhaust leak or flex pipe leak. There seems to be a roar like rattle or vibration going through the exhaust system. But I replaced the complete system from the manifold gasket to the tail pipe. I am getting a few error codes. P0300, P0301, P0303 and P0305. I even swamped the coils and plugs out no change, still have the noise. The vehicle does have 190,000 miles with Auto Trans. No oil in coolant or water in engine oil that I can see. I have done a compression on all cylinders they are all just above 125 PSI. Wheel bearings and axles all seem fine. The engine is probably on its last legs. Just has me puzzled. Thank for any help.