V8 LifeStyle

Hey guys really quick. I just installed LTs with true duals 2.5 inch system which goes from headers to x pipe to two cutouts then two magnaflow round mufflers dumped at the axle.
Tomorrow im gonna have a shop do custom pipe under the axle (like that shop in texas dpes). My question is are my cutouts gonna really make a power diff when tuned for.running open cutouts compared to no cutouts and tuned properly. (My system is a free flowing system expect for a few bends (x pipe and pipes from mufflers to rear bumper)
BTW car has trick flow 195cc heads/CC465/ edelbrock intake manifold /58mm TB/CAI and tunning it myself. Thanks