Here is a link says vacuum does affect fuel injection.

http://fordfuelinjection.com/?p=93

By the way, all engines are supposed to compensate the idle for power steering and AC, maybe there is a consistant leak instead of what you mentioned in the brake booster, cause that leak should only affect you when you press brake pedal.

Guess first thing for you is to fix the vacuum leak, then see if you need a tune up.