It is normal, all of them have it from the factory.
really? do you know why? whats the reason for this constriction on one pipe and not the other?
2013 V6 Mustang Automatic with the following mods: Roush Hood scoop, 3M Clear braw paint protector, MRT rear window louvers, 3M scotchprint carbon fiber roof wing decklid and scoop, strut tower brace, FRPP axleback exhaust.