Hi,
In camera raw processing module in PS find section responsible for noise reduction (section 'Detail', under sharpening). There are 2 sliders - one for colour, second for luminance. As far as I remember luminance is always 0 by default, so - on 100% view - change to 30-35 and check results. In your case - you can start with colour's slider and then apply luminance, slightly less.
Pav