Hello Everyone,
First post...
I've got a 2016 Altima 3.5 SR and within the first dozen miles of driving it I installed a K&N Cold-Air intake system and immediately noticed a dramatic increase in responsiveness, power, and sound of the engine and exhaust. I brought it back down to the dealer the next day and showed it to the salesmen who sold it to me, and a few others who got curious, and they were all drooling over it.
It's a Typhoon Air Intake model# 69-7063TTK and can be easily found online (Amazon / eBay / Autozone / etc.)
Took me about an hour to do - time well spent!
Hope that helps...
Dan