Vehicle: 2004 Expedition, small V8 (can't remember size, 4.9L maybe).
Problem: When A/C is on it will blow to defrost when RPM +1k, then will switch back to blowing normal when under 1k RPM.
Reason: Leak in my vacuum lines somewhere (or so I've read).

Questions:
#1) Which lines are my vacuum lines? Pics or web links much appreciated.
#2) Where would this leak most likely happen? Joint? middle of hose?

I am by no means a mechanic, but I am comfortable changing all fluids, alternator, brakes, etc, minor stuff. So you'll have to pardon my ignorance as to which lines to examine.

Thanks for any help.

 

See the FAQ above for a starting point.

 

/bump
since the only response was extremely useless