Definately Stillen G3's FTW...Was also looking into this issue at one point in time, but after looking at all the independent reviews their gains/numbers came out pretty consistent.
I've definately seen/felt better throttle response, and you can hear the difference of the motor when reving past 5K...If you have an aftermarket exhaust you won't be able to hear it, unless you're outside of the car.
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2013 Nismo Z34 / FI TT #091 / IG: @lilzilla_z34
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