Ok I have a 2008 G37 Coupe 5AT with 18" stock wheels
I'm going to buy some parts from a guy on facebook
-Eibach springs
-20mm spacers from 180
He is also selling shocks from koni yellow, My questions is do I need the koni yellows? or will just the springs be ok? He said my struts will go out if I don't use them, is it true or is he just trying to sell me this part?

 

The eibach springs will accelerate wear on your OEM struts, but it's not like they're going to instantly blow out. The Koni yellow struts aren't immediately required. However, with a 2008, you might be close to the lifetime of your OEM equipment and it might not be a bad idea to pick up the struts.

 

yeah my car now has 73k miles maybe I will buy them then, thanks

 

Another bonus is you can keep your OEM struts & springs together so you won't have to go through the removal of your OEM springs and if the Eibachs are already installed onj the Konis it'll make installation a breeze.
Also good to keep your OEMs together in case you want to go back to stock to resell the vehicle at stock height.

 

Depending on whether the Eibach springs are the Pro-kits (low) or Sportlines (VERY low); your dampers (shocks) will be under more stress the lower you go.