Having a flat splitter avoids creating a pressure differential making it easier to control boost. I have seen "RMS Dump Pipes" vary subject to the customers budget.
The pictured dump pipe is very similar to the Perth Exhaust Centre item with its small waste gate collector + splitter. Better than OEM but not in the same league as MSR imho.

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Speak to Shane @ SMC Tyres, Unit 6/385 Sevenoaks St Beckenham WA 6107. Mobile 0413 128 087. Tell him Maddog sent you!