My Roush Exhaust not loud at all

[Hafiz3.7L]

Hi guys so i just bought roush exhaust and applied it to my 2016 mustang v6 and there is barely any difference my friends 2013 s197 sounds WAY louder without anything but the exhaust i don't know how i can fix this and also when i rev the car in PARK MODE it only goes up to 4000 RPM and goes back down to 0 someone please help me on why my roush sounds so quiet