A Ram air style hood will force air under the hood, however for us LSJ guys there is little to no benefit in doing this(save for the redline, which comes with a SRI, as opposed to our CAI style setup). Having a vent pull hot air out is more beneficial for cars that pull in the intake air from outside of the hood (Drivers side fenderwell for the cobalt LSJ). Now for the 2.2, and 2.4 guys, as well as anyone running an under the hood filter you will benefit from a properly placed ram air design, as it will get more cool air into your intake.

When you say "suck" the car down, I assume you are talking about downforce. I don't think there is a hood on the market that would be able to provide any noticeable gains here. Typically front end downforce is achieved through splitters/spoilers and/or canards, which can all place more downforce over the front axle.