FWIW, we fitted our headers & cat + 2nd hand mugen twin loop.
This was to a bone stock EK4 VtiR.
Starting power was 88kw @ wheels...
After fitting system... 98kw... (+10kw)
Not bad for a 1600cc engine.

Dynoed in shoot 4 - Std aribox, std ECU, ignition timing set factory 16deg.