My favorite is the Yoshimura style 4-1's. I'm sure real ones are the best, but I've never heard one. Carpy sells a pretty nice version, that has a decent baffle for the street. These bikes can sound really mean at high revs with a few mods. I have an almost brand new Hooker 4-1 I'm going to try after I rebuild one of my motors, so I can't comment on that one just yet. The stockers look and sound sooooo good, but they're really expensive, and can look out of place on a modded bike. Used ones are usually rusted straight through, or on their way out, so they're not such a great option when looking for stockers. I've heard a few different 4-1's and 4-2's. My '71 500 has some '80s Honda sport bike muffler welded onto an unknown chrome 4-1 header. I like the way it sounds, but it's ugly as heck. The Mac is the easy replacement. I'm not fond of the way they look or sound, but that's my personal, very subjective taste I'm stating.