If your talking about the stock replacement K & N filters its worth it. I know this site has plenty of jerks on it that can only bad mouth things rather then help answer the question.

Yes you buy two filters, they are sold individually.
Here is the part number 33-2399. Take this number to a parts house like autozone or something and they can get em for ya ......... might be called stock replacement filter in thier computer but its the k &n's. bout 46 dollars a piece.
Did i notice a difference, not really. But its better then an open intake in the hot engine bay.
It will not make a noticiable change in intake sound either.

 

Theres no gain with replacement panel filters for the airboxes on an VQ35HR. Period. The advantage is the ability to clean and reuse them. Its a tough call though, stock paper filters are 12 dollars each vs. 46-ish per K&N filter.

TK

 

I replaced mine, and loved them. Put about 2-3k of miles on them so far.

 

There probably is a LITTLE gain, but hardly anything noticeable.

 

I got both of mine from the Z shop for 73 bucks