welcome tpaul
i put a Dubach muffler (Dr. D) on my bike,and i love it,,,it gives it a deep throaty sound,,,not rappy,or irritating,,,,it is however louder than stock,and there is a gain in HP,,,,its very well made,and was easy to install
a little advice,which ever pipe you end up with,,,,go to the auto parts store,and get a 1 1/4 exaust clamp,,,and go to Lowes (or like) and get 3 large hose clamps,about the same size as you use on the back of your Cloths drier,,,you will need the hose clamps new when installing the new pipe with the stock heat shields,,,and the exaust clamp,because the stock one wont work with the new muffler
this will save you a trip to round these things up once you start the work
one bracket is spot welded to the stock muffler,,,you will need to use a cold chisle to remove it,and grind the spot weld off to reuse it,or order new from Yamaha (i reused)
also i too use the K&N air filter,pro flange,and outerwears,,,,,to me,there is no way dirt can get through,as long as you maintain it clean,but cleaning goes for all filters,,,,its the flange setup that is impressive