An easy way to test vacuum systems is to blow smoke into the lines. If you already smoke that's easy, but a $1 cigar from the gas station is perfect. Just blow it in and look for the smoke. If it's in the lock system then you probably won't find it that way is all.

I've noticed that on this board the most expensive things are often suggested first (Runs rough? You gotta pull the engine and buy a brand new one!), but seriously, look at the easy and cheap stuff first.

-Rog