"Warranty" first service check
 

I boght my 2012 in 2013 new with 90 miles from the Nisan dealership.
I'm at 20k miles and called today about going in for my first service check. I kinda fished around by telling him I had like 18k maybe 20k miles and how would that affect my warranty. He said it really needs to be done before you get out of the teens. But said it might cost more if it's 20k and void certain aspects. I also asked, so what if some one had like an aftermarket air intake on it. He was like if you have any mods it "could" void the warranty if a problem is related to the mod. So first of all should I put my old filters back on? Second of all are they going to screw me for having 20k miles. And 3rd are my tires and brakes covered under warranty? Front tires are bald and front left break is squealing. What is my best action? I get my oil done regularly with mobile one full syn.

Tires and brake linings are normal wear items not covered by warranty. If you done oil changes, you should be OK. If they want to suggest your CAI intake is a problem, immediately them that you see that you're giving your business to the wrong people and will not be returning.