RE: Check Engine Light Vacuum Leak
Best way is to get a handheldvacuum pump with a gauge on it. Basically you start at the manifold and throttle body, unplug a line, pump it up to 20psi, and see if it holds. Go to the next tee, disconnect the two lines going away, and repeat the process on them. You can also use a vacuum gauge with the motor running in much the same way. Its just harder to trace out the exact location of the leak because you have to work backwards.
You can check manifold leaks with a propane torch. Point the unlit stream of propane around the edges of the manifold. When the rpm's jump, the area you are pointing at is the culprit.