If the vacuum line to the opti isn't plugged in, could that cause the opti to fail?

 

It would be the equivalent to the non-vented style optis that are prone to failing sooner than the vented style. The vacuum line sucks fresh air through the opti; source of the air is from your intake ducting (just before the TB).

 

So then the answer is no, it wouldn't cause opti failure... thanks man.

 

but it will cause a vacuum leak cus one end is connected on the bellows and intake manifold and the other side wasn't connected

 

Your opti WILL fail sooner because you're not venting it.

 

Would cause the opti to perform poorly?

 

Is the line plugged at all? Could be getting dirt in the Opti.

 

It wasn't plugged in at all... just a big vacuum leak.