If you look in bios, should be under the advanced tab, there should be a listing for the peripherals, that includes the usb settings for off, partial on or full on. The problem there is if you set for off, USB isn't enabled until after post, so with a USB keyboard, you'll have a hard time getting into bios to say the least. Partial on will activate some of the usb at boot or shutdown, but if the keyboard isn't on one of them, then again you get stumped. Full on is all USB ports on at post.
Asus also has dedicated charging/on ports. Asus has a specific green labeled USB that's always on, regardless of bios settings. This is used for fast-charge and bios recovery/update without cpu.
There's also usb settings in windows power plan, turn off all the 'wake timers' except kb/mouse.
Push come to shove, just swap the mouse/kb to a different USB port in the rear until you get one that does what you need.
The EuP settings are located under Windows 8 settings in bios.