We make a lot of basemap files for customers, and many times because of the number of variables involved your basemap might be overly rich or lean...especially at idle.
The EASIEST place to fix this in a overall fashion is the overall FUEL TRIM Tab. Use this in whatever ECU or Fuel Management you are using to increase or decrease the fuel to give you the best over all basemap idle/cruise air/fuel rations. Raise or lower these 5% or 10% at a time, and in the real time updating ECU, you will immediately see a change. In the Flash based systems you will have to reflash the ECU until you get it close.
Basically just get it the ECU to idle and cruise in the 13-14.9 range....not too rich, not too lean.
Here are some basic instructions on where to find these and how to update them.
Parameters --> FUEL TRIM --> Overall Fuel Trim