2000 camry LE I4 injen intake problem

i have injen intake for my 2000 camry I4 and i saw there is like a hose is unplug and i think is vacuum hose.
so my questions is should i plug that vacuum hose back to the intake pipe or just leave it? what is that vacuum hose anyway?

p.s. if something wrong with the intake system does the "check engine" light pop on?

thank you