the jdm 4-1 has a 2.5 in collector. you'd have to have a new 2.5 in flange welded onto your stock cat for it to fit, or get a new high flow 2.5 in cat. then it would flow into a 60 or 60.5 mm exhaust which is a bottleneck for the system. how big is 60.5mm and 60mm? (damn metric system h: )