It's hard to say how much power was gained considering I never dyno'd my car. But it definitely made a noticable difference

 

I've had a GReddy SE dual, J's Racing 70RR, and the EVS. The EVS was by far my favorite, although I had issues getting it to fit properly to keep it from banging the subframe. All were paired with a stock header and 70MM test pipe on my AP1. The EVS did have some drone but it wasn't terrible. The sound at WOT was intoxicating though, and you would get a nice gurgle when you let off. As far as whether it added 13hp...no idea. I suppose the 70RR probably gave the best hp increase but we are talking maybe +/- 5hp from each exhaust...at the end of the day you won't notice it.

 

Quit fussing around with a few HP differences in exhausts. If you want to unleash the true potential of these mods get Hondata or AEM EMS then a tune. Done Deal.