Zoomies on a non blown car are just throwing horsepower away. This is a well proven fact in the world of exhaust design.
In the early 80's we tried them on my dirt late model to kill torque off the corners in a attempt to control wheel spin. The only thing they seemed to do was create so much dust in the car that you had to use a tear-off just going across the pits! Used them one race and then sold them to the first person that showed a interest. They did sound like **** but if they would of worked I would'nt have cared but they seemed to kill horse power through out the rpm range not just off the corner.