resonator delete break in?

Just got a resonator delete, kept the mufflers. Was expecting it to be slightly louder but honestly sounds the exact same as before. Ive heard people say it takes time for it to "break in" and get louder. Is this true and if so how would a pipe get louder? Is it because without the resonator the mufflers have to "work harder" and the mufflers break in more creating a louder sound?