seeing as its auto.. maybe a dr drift remap??
oh yer.. i make all my own exhausts.. funny enough silvia's exhaust is quieter than a 3inch turbo back system on a r33 gtst
not very good pic but you get the idea..
twin 3inch dump/fronts 4inch in/out metalcat(5inch bod) jun 3.5inch muffler
it has a very very nice note!