another note regarding the apexi header is that it comes as a set with the OP and FP and since the FP has a fairly large resonator on it, it makes for a much quieter setup even compared to stock when pairing with various aftermarket catbacks @
mav1178 posted an in depth review here
https://www.ft86club.com/forums/showthread.php?t=103338
I personally run this kit + fujitsubo catback and it's quiet enough that I don't get harassed by cops