AMD issued the Radeon Software Crimson Edition 16.5.1 Hotfix driver, you can download it over here. This release has optimizations for Forza Motorsport 6: Apex and promises up to 27 percent more framerates than version 16.4.2.
Radeon Software Crimson Edition 16.5.1 Highlights
Forza Motorsport 6: Apex™
Performance increased up to 27% versus Radeon™ Software Crimson Edition 16.4.2 on AMD Radeon™ R9 Fury X(1)
A few game titles may fail to launch or crash if the AMD Gaming Evolved overlay is enabled. A temporary workaround is to disable the AMD Gaming Evolved "In Game Overlay".
HDMI™ Scaling options may not be available in Radeon Settings on some system configurations or some applications may ignore the HDMI™ Scaling options setting.
The option to enable/disable AMD Crossfire™ technology logo may be missing on some system configurations from the Gaming, Global Options tab in Radeon Settings.
The Witcher® 3: Wild Hunt inventory and character pages may exhibit flickering in AMD Crossfire™ technology mode.
Radeon Settings game manager does not display icons for Origin Games.