Hitech in Sydney will be your best bet for quality for quad mufflers. Get the y and centre pipes fabricated locally. The location / design of turbo and manifold means you wont get any dak dak sounds but you should get much better torque across the range if you believe Subaru. Nobody will have dump pipe available for awhile will be my guess. Try the usual suspects in Japan for springs and coilovers.

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Funny looking German Subaru