I just contacted the shop I had it done(NPB Muffler) The manger is being a jerk he says there would be no difference in interrior noise with the delta flo 50 series. He doesn't believe what flomaster says... and he wouldn't install a 50series for the difference in price! Flowmaster suggested I try exhuast wrap on some of the piping and top of the muffler..?

Thanks guys for your reply... this is a cool site.
PS I haven't had a chance to noticed the performance increase because stepping on the gas is sooo loud I am amazed by the noise alone.