Possible vacuum leak?

[Zach0112]

So, I've been reading through here and Gagt and I think I may have a vacuum leak. I have a low rpm surge, below 1800ish rpm) that gives a trailer hitching feeling going up hills. While driving easing into the gas it seems low on power and when you hit 2000 rpms the engine note completely changes. Not just because it's spinning faster, but almost sounds like it smooths out or something. You can feel it pull so much more right when you hit 2000-2100. Kinda like a boost of power. While I had my hood open tonight I could hear a Sucking sound. At first I thought it was my wai, but on further inspection I noticed it was coming from the passenger side. So I started working the throttle and the Sucking sound would get louder, louder than my wai I think even. Sounds like it behind my ps pump and just to the rear a bit. Can't really see down there, but are there hoses or anything? I sprayed starter fluid down there with out a change in engine sound. Seriously sounds like I have a filter tucked in behind my pump, it's that loud. I'm also getting 27-28 mpg with the 3.4 with spirited driving. It's strange if it were a vacuum leak that I'd still be getting this.