exhaust whistling...

[kchu221]

hey guys, so i have the amuse r1 extra titan exhaust and the amuse r1 front pipe, but during lower rpm's or after i rev it a little and the rpms are going down, theres a really annoying whistling sound coming from my front pipes, does anyone know if the sound if normal or did i get a defective y pipe..? my installer also confirmed that the whistling was coming from my y pipes, but i wanted to ask you guys first before i assume anything... the reason im asking here is cuz theres only 2 amuse exhausts in the us for G37 which is me and another guy on the other side of the country but doesnt have the same setup as me, so i dont think ill even get any answers on that forum...