I took it as a street car with an almost stock, or stock engine. Without dyno time, who knows what the power level is. He didn't say headers, or not. I just remember back in the day how good a big wedge sounded with a stock H pipe system. You can cruise for hours without the noise, but step on it, and then you could hear it. The bigger everything is the harder it is to hide, so I thought 2 1/2 would be big enough for a stock street car.