The idle mixture screw is hidden under a soft plug on the underside of the carb. Most guys report good results with it in the neighborhood of 2 1/2 turns out from fully seated as a starting point on the later CV carbs like yours.
If you're running white do the usual checks for manifold leaks, etc. and if none are found it may be time to rejet.
Your neck of the woods is so close to sea level that you should have a lot of latitude for main jet increases. Very few have ever found the need to up the pilot jet.