It's pretty subjective. What do you consider slightly louder? The noise difference between Nismo and stock exhaust is not going to be very noticeable. May not be loud enough for some and may be perfect for others.
Your best bet is to find someone local with the same or similar setup so you can hear it in person. There are a lot of videos on youtube also.
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2011 370Z 6MT Sport Gun Metallic | ARC | CJM | Ecutek | FI | Fujimura | R2C | SPL | Stillen | TWM | Z1 | ZSpeed | |