Which vent on the Opti do i run a hose for vaccum and where should i run it to get the right amount of vaccum. What will happen if there isnt a vaccum being pulled on the OPTI. It is a 96 camaro.

 

If no vacuum then condensation will build up and mess up the optical sensor. My 96 got the vacuum from the driver side of the manifold, through the thinner of the 2 hoses, the one hooked up to the metal nipple on the opti, NOT the plastic one. The other tube hangs behind the opti IIRC and just works for intake air. If you can source one of those little inline filter-jobbie-dos (looks like a spaceship about the sice of a quarter) I'd put one on the end of the inlet (larger tube.) I did this and so far haven't had a problem.