you can make your own with best of both worlds.i made my mufflers with 3" perferated tube wrapped with ceramic wrap then slide a 4"tube over then make end caps (4"diameter with a 3" hole for tube to fit thru)weld up and the larger the perferations the quieter itll be.mine i made is 36 inches long with half inch holes.fairly quiet (especially for a bullet style muffler)no probs with police yet
ive never tested but would imagine any thru muffler will flow more air than a chambered muffler!id have to say its hard to hush down my 572 with a thru design muffler but mine works great.next year wanna test against open exhaust at track to see what it costs for hp loss (hopefully not much)any questions pm me...russ