Vacuum leaks can be VERY sneaky. On one car I found someone had used way too long a bolt and smashed into the core plug at the front of the right intake runner. On another car the "O" ring for the CSV was missing. Injector seals are very common leaks. For temporary just wrap the seals with Teflon tape. ANY leak bypasses the air sensor and leans the mixture. On one car the springs on the decel valves were overheated and the valves were leaking. Someone has to go over the whole motor from top to bottom and find and fix everything just so to get it to pass. Just not pushing an ignition wire on tight can fail you (or if you pulled on one you broke the core inside). Or maybe the timing is not set correctly. There are just too many things that can affect the emissions for any of us to tell you do this or do that.