Howdy. Distance repair is difficult, but it sure sounds like a vacuum leak especially since there are no codes.
Another way to check to see if you have a short or open on the pwr steering idle up circuit is to hook up a tach on the engine, be in a neutral position (sometimes you have to be in a geared position), and turn the steering wheel all the way to one side or another. Generally speaking, the PS idle up circuit only works at the extreme ends of the steering rack, or "lock to lock". You should see at least a 50 rpm difference between your steering wheel being in the center vs. at the lock. How's the level on your fluid?
On the intake manifold gasket, Joel is on the money. You don't want to use WD-40 or brake cleaner. There are 2 same things to use, one is carb cleaner, the other is simply water. Yes, water. I personally like water because I'm a little sensative to carb cleaner. Also, water is free and doesn't evaporate as quickly, which can be helpful at times. If you do use water just make sure not to dump it on, i.e. use a spray bottle. If you dump it on there and let it build up (particularly with cold H2O) you can crack the manifold. The same thing can happen if you do water-crossings when 4 wheelin'.
ASIDE: I know there have been many posts on seafoam, and it certainly has it's merits. However, water can be shot directly into your intake manifold and "steam clean" the cylinders. Just raise your RPMs and use a spray bottle to mist the water in the intake. Don't add too much or your hydro lock your motor. Anyway, you'll see some carbon spit out your tailpipe as a result of the steam cleaning. An old farmers trick.