On my 4/4 I had a full Librands system, manifold, sports cat and exhaust and lived with it for a couple of years until I found it just too loud on long journeys. I replaced the straight through 'silencer' which is simply a stainless tube with no silencing at all with the Librands acoustic muffler and it just took the edge off enough to make longer journeys more comfortable but was still plenty loud enough for me. The 200 cell cat definitely flowed a lot more than the restrictive original.
Have to say though the straight through non silenced system sounds glorious if you can live with it.
