That's strange! I'm under the impression that most straight-through mufflers would be the least restrictive and that the UltraFlos are among the best flowing ones out there. But not all mufflers are created equal. I'm curious what brand bullet mufflers you were using. Perhaps the UltraFlos were actually less restrictive and changed the carb calibration requirements because of less back pressure? Coincidently, I'm putting a set of DynoMax bullets on another car I'm working on to save weight and provide more room around the center section & driveshaft. Unfortunately I'm not in a position to do back-to-back tests. But I wouldn't do it if I expected a performance loss.
