Hi,.......Looking at your photos of the exhaust system, what I think seems to be missing is a "Balance Tube " between the two exhausts to cut down on the resinance ( Loud noise, Echoing, drone if you like ).This was told to me way back in the '80's, I found it to work o.k. Best place to put one in, would have to be where an exhaust person can weld all around at both ends without too much trouble, keeping as far forward as possible, all this easier said than done and another small headache for the exhaust man, oh by the way an excellent job on the exhaust set-up, good luck ......................John