My 2004 Infinity FX35 when idling it feels like its going to stall out.

That engine is equipped with a Mass Air Flow sensor. Sounds like it is either dirty, broken or you have a vacuum leak. Most likely dirty. They are easy to break while cleaning if you aren't delicate with the wire on the inside of the unit. If the computer doesn't know how much air is entering the engine, it can't add the correct amount of fuel. A vacuum leak would allow air to enter behind where the sensor is measuring, so it's like air sneaking past the gaurd and entering the engine. You would have extra air it that isn't accounted for so the computer wouldn't add enough fuel. A vacuum leak will typically sound like a loud hissing in the engine bay.