Now, Im not very versed on the 05's, but that sounds like an Idle Air control valve issue like we have on the 99-04's a lot. If your car has one of these, try checking it (cleaning it out with brake cleaner). Now, how many miles does your car have, because this usually doesnt happen until the car gets about 40-50k miles on it, but thats exactly what it sounds like. Also, do you have any mods and not a tune? Maybe that could be some of it. Need a little more info.
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