to redirect the exhaust flow from the original flow to shorter exhaust flow.
So , like using straight piping without muffler la after the valve open coz the air will go through the new hole.
Our Ketua Darjah's awesome ER34 was recently sighted at TAS 2011.. Now sporting a GT-R emblem at the front.. Senyap2 dia fully convert to GT-R spec.. :biggrin...