The ASP crank pulley is made from a stock crank pulley and is dampened. The EC is their customed made crank pulley with no dampner. You can research on MBWorld.org whether the crank pulley should be dampened and form your own opinion. It's half and half. Something to do with the vibration. The other pulleys in the kit are basically the same. ASP uses a steel water pump pulley, EC uses a strong aluminum. The ASP and EC idler pulley only differences are that the EC has an upgraded bearing to withstand the rpms that the 181 and 185 crank pulleys demand. As long as your staying with the 178 your in a win win situation. Just add a needswings intake and inmotion tune and your good for low 12's.