basicaly... those exhaust u found stamped with the JASMA thingy is usually brought in country fm japan by halfcut shops etc. its a governing body in japan which has a certain levels that a mass production tuner muffler has to abide in order to meet the set standards i.e noise levels etc. even if u bring in a car which is meant for japanese market, ever notice that the oem speedo is only up to 180km/h (its the rule in japan)
i've seen an apexi N1 exhaust sold by speedworks pj(official distrubutor) which has no JASMA....why, its coz the exhaust is made by apexi to be sold outside japan so no requirement for it to pass japan law in that specific matter.
only thing is that some of us have the perception of "wah...got jasma very good, no jasma no good" it has been like some kinda icon to some of us. maybe to some extent if u think abt it..yes the exhaust with jasma tag has a considerably lower db levels....but thats only if u get the fool head to toe system.
one think to ponder... IMHO, its not the tag or the brand....its what u can get to extract full potential of ur engine with regards to exhaust system. but then as the saying say...no muffler at all is the best, but i'm sure the car u have is not a racing car...so noise levels is also a thing to consider.
just my 2 cents
