Love the Viper shot. What I would suggest is to use a bit more contrast and exposure to bring out those light and darks When the suns out. When its dark out, I would suggest lowering the contrast a bit, and raising the exposure.. but you seemed to get that part down on the viper shot. Also, check out this tutorial I wrote up for FM4, it will work exactly the same on Forza Horizon. It explains how to use the Aperture/focus.
Link here<<<
Great shots man! I can't wait to see what comes next