I removed 160SR duct today. It's all the way from intake to air box about 54mm in diameter. I found two intake silencers, most likely to muffle suction noise in drive by noise test, in duct. When I installed cold air induction to my Camaro, instructions told to plug or remove silencers, in order to avoid turbulence in air flow. I tough follow same principal with Micra and taped silencer openings in duct, I left silencers in place. Bigger one has mounting post for duct. This modification took about hour. I don't know is it my imagination, since something was done. But throttle response seemed to be little bit crispier... 
