Our single through 3 inch full system has zero to 1/2 PSI back pressure at 25 PSI boost. The Exhaust cools as it moves farther back and requires less room after cooling. I have taken off the muffler section on the dyno and it offered zero gain. I also have had 2 customers with cutouts and both made the same power open and closed. I also removed the muffler sections at the drag strip and I realized zero gains in ET or MPH. Removing the muffler sections will only increase sound if your running full 3 inch.