the red pipe is part of the EGR system. it has to do with emissions during warm up but is often removes as it serves no purpose after warm up. the blue looks like a heat sheild. Just remove it if your want or keep it. doen’t really make a difference. i beleive its called and AIR pipe or something.
For me its a matter of bolting on the exhaust myself, or paying someone $60 to weld it on.
I looked further, theres rubber hose connecting the red pipe to another pipe going to where all the emissions stuff is. If I do decide to remove it, should I just plug the hole somehow?
That isn’t egr. It is aav or some crap. Same difference. Nissan engineered it so that it would make it more emission friendly not to make the car run better.