Driver issues Windows 8.1 Pro on Late 2011 MBP
Technically speaking this might be best asked on a Windows board but...

How did you update and reinstall the drivers?

I would download the latest BootCamp drivers and then go into device manager, find the devices in question and right-click on them and select uninstall. Simply reinstalling often doesn't fix driver issues, you gotta remove the old ones completely first.

Once the problematic drivers are uninstalled reboot.

Windows will likely detect the missing drivers and reinstall them from it's cache. If it doesn't use the drivers you downloaded from Apple