Yup, I too found out the hard way. I had a complete dg exhaust on my 350x, but whoever owned it prior to me did a horrible job of installing it and basically ruined it, so I bought a brand new cobra exhaust system. I have hated it since day 1. It is anoyingly loud and does not even have a good tone to it. I also jetted the trike to run correctly with the exhaust, but noticed a very negative change in performance. So, with all of the engine mods I am doing I have decided that I am going to fabricate a high flow header pipe and use a 450r muffler. I will definately be selling the cobra system. I would not reccommend them to anyone.
'86 350x
'05 sportsman 500 (the couch)