The engine on my fiancee's 2000 Neon has been acting funny lately. It basically makes a noise as if there was an air leak or something wrong with the idle control valve and the car is going up and down in revs. I haven't noticed the revs actually going up and down but the noise is definitely easily seen and I have no clue where to start looking. I was thinking the alternator might be going out but again, no clue. Any help is appreciated.

 

Vacuum leak?

 

check along the underside of that accordion breather tube seen tons of em with a split in it

 

...and the PCV line.