If you implement properly the Image Based Ambient Lighting (IBLA), and you add proper convex hulls around your track, you'll manage to get better ambient light/color in the occluded areas, like those you posted, or tunnels, garages, under trees etc... It's important to find the better spot for the global probe, and then produce hulls around the track, where you need them. Place your global Probe in a place where you have a good overall view of the track, not too close to occluded areas. Always better to place the global probe on top of tarmac, with all the grass around. After that, try producing small convex hulls, and place them in the "hot" corners, those that will receive longest shadows from the mountains. Give them proper Influence Ranges, so that they will mix smoothly while you drive around. Place those hulls in the middle of the tarmac, center-line, something like 1 or 2mt above the ground. You can use the IBLA "debug" tools you have on mod dev, to preview every single hull, and see how they are working, and where you need to change/improve.