Hey Juan,
Yes, there are always more vacuum lines than just the one from the PCV valve. For instance, two that are pretty critical to your car working are those that go to your fuel pressure regulator and brake booster.
The rest of them, like evaporative emissions, exhaust gas recovery and idle air also generally connect to the intake manifold, which is under vacuum from the engine. The immediate problem for us with that is that however well sealed those items and their connecting hoses are supposed to be, they often leak when they're "off", weakening the engines vacuum which reduces combustion. Thus, we look for ways to reroute them to restore engine vacuum, or cap those that won't piss the computer off and cause it to throw error codes.
As for not knowing where the vacuum lines go, just visually follow them from the intake manifold to whatever they connect to, then look that thing up in your manual and you'll have the answer.