I have the dual on both the cars now. I started out with the single on the roadster. There is a slight increase in performance. I had more low in torque and it gained me a 1/10 or so in the 1/4 mile. But a single would serve most people just fine. I am not much for dynos. They all seem to tell you different numbers. I am one who likes to go out test it in real time real parameters. When we changed out the single for the dual in the parking lot of the hotel in Detroit, and then headed right back out onto the interstate, there was a noticeable difference. That is all I can say.