Both are very close to each other. For these cars, it seems like Y-pipe style exhausts make the best top end.
I compared a dual 2.5" exhaust w/ an X pipe to a motordyne style exhaust with a 3 inch mid section back to dual 3inch and it picked up about 6-10 whp.
In theory, the dual 2.5 inch flows more but the Y style made more power.
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Creator of the GTR TT Conversion Kit, NA Record Holder (401WHP)
Ecutek Master Tuner (VQ37, VR30, VR38, B58, S55, S58)
BTWTuning
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