Rang what is wrong with a S2000 muffler...I bet internally it is close to the same design as an ep3 muffler and it still flows well enough to produce more HP than the ep3 does. S2000's throw down higher numbers than an ep3 on the dyno and are proven over and over that exhaust swaps don't really net anymore power. Therefor, the stock muffler can't be too bad...it is enough for 200whp out of a 2.0L.