Originally Posted by rjk

I would search out the smallest vacuum line that enters the throttle body AFTER (below) the throttle plate. That should ensure a relatively even distribution to all cylinders. Usually a hose to a charcoal canister works well (if your model has one).

If you feed it at an extreme end of the manifold, it may not get to all the cylinders equitably.

As stated in an earlier post, don't feed it into the intake system above the throttle plate (the air cleaner side). You want it to atomize and coat the parts. The further it has to travel, the more likely it will find a place to pool (like where it would bang into the closed or barely open throttle plate).