Nicely done, Justin.
Personally I am sure that a good aftermarket up-pipe (like the GS one) would result in an increase in power over the factory catless one, especially with bigger turbos. But I don't think that flowbench numbers are the absolute last word in which one is "better". There is the velocity factor where higher velocity is better, and a bigger up-pipe will have lower exhaust gas velocity. Also there are up-pipes on the market that are likely too big in diameter, which would probably "flow better" on a flowbench, but they might be worse because of the lower exhaust gas velocity and the mismatched diameter steps at the inlet and/or outlet of the pipe.
The Grimmspeed up-pipe is a nice design that avoids the flow-killing step-up/step-down and is about the right size for most applications.
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