My air filter is not good need 2 be replaced .

I was putting techron system cleaner and no change.

So i will change pcv valve ? U have got location ?

I will put new system clean and change air filter soon

 

PCV valve is Different for 4 cyl or 6 cylinder and i'm not familiar with that year, and yes after 5 years it needs replacing.
Hopefully Grim reaper chimes in as i'm sure he knows location, but need engine # cylinders, size would be helpful and your location country.

To see location on my car, 2006 3.0L V6 click on to view pics: Mazda Forum - Mazda Enthusiast Forums - UseYourNoggin's Album: Intake Plenum & PCV Valve. 2006 Mazda 6 V6 3.0 ltr.
PCV valve is near egr valve, in intake plenum, slightly behind it and to left when viewing from front of engine.

 

Ok i will update after going to dealer for pcv valve