Ford Repair: 99 ZX2 wont run, vacuum leak, vacuum line

Question
It started as a rough idle. I had the check engine light looked at and it said the car was running lean. You can hear a sucking noise from the back of the engine, kinda around the throttle body. A couple hoses look old, but I couldnt find anywhere that should really be leaking. I checked the manifold, no cracks, replaced the manifold and TB gaskets, and the injector O-rings. Got new plugs and wires as well. Have double and triple checked the the wires are properly seated on the plugs. Is it possible that a tiny crack in a vacuum line that doesnt even appear to go all the way thru could be creating a problem so big that the car wont even run? Is there something else Im missing? Maybe a bad O2 sensor or MAF sensor? If so, how would I go about checking these to make sure they are working? Sorry, I know this is long winded but any advice you can give would be greatly appreciated. Thanks!

Answer
I see where you through a lot of parts at the vehicle. I could use a time line. In your message, you say won't run. But in your description, you started with rough idle. Lean code was kind of vague. Did it say anything else. Do you have the ability to retrieve the actual code itself? If it is a standard lean code, one would think MAF, but you also have the sucking sound. You have to find where the sucking sound is coming from. If it is not running now, after the parts that you installed, check all your connections. The car, even with a vacuum leak, should still run. Run down to the parts store, buy 3 foot of each size vacuum hose they have in stock. There are only four sizes, so you should be ok as far as money goes. Take a look at the vacuum hose going to the brake power booster and make sure it is snug. Also look at the check valve that connects the hose to the booster.