you can get your exhaust downpipe seperated to block the wastegate emissions entering the exhaust then you would have your exhaust pipe say 2.5 or bigger 3" and then your screamer pipe next to it usually 2"s has a good sound directing towards the ground preferrably after or pointing away from the sump. I have had a 3"down pipe with 3"dump/screamer pipe and the sound terrorfies passerbys and hmm hmm fellow motorists but also a 1.75"pipe screams enough or should i say roars enough (sounds similar to a jet plane on heat whilst on boost)