In most states bikes don't have any noise regulations, that's why they don't get pulled over.

 

Picture of my 'Fake Cat' (it's straight through, not open, just a piece of pipe with a shell welded on. Bought from Votion)
And my Schoenfeld muffler. (also straight through, not doing much muffling, have two on my Late Model, decided i'd put one on my header for a couple less DB's)
Both being welded into my header.