If its the same Prodrive back box as mine then it's a 2.5" system. A 3" resonated system would bring up the rumble and sound louder. If you want it even louder, take out resonator, and even more louder then a decat downpipe (will fail nct then). Without a resonator, it will drone at motorway speeds too.At the moment I have Prodrive exhaust and im not too sure on its sizing.
But id love a louder exhaust [emoji846].
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Best thing to find out whst you like, come to one of the meets, and hear the different exhausts on the cars[emoji1303]
Subaru Impreza Wrx SL Wagon 2004
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