turbo sounds different back pressure building

[Mustangr]

I recently put on a 67mm turbo on my stang. The sound of my car is totally differnet than with the s/c. .....QUIET.... Anyways, I think im getting some back pressure causing alot of crankcase ventilation problem form my 15 year old dyno max system.
What would be a better exhaust system???? Remember I like my new quiet car.
Thanks, JASON