[GUIDE] Downgrade stock 6.3.3 to rootable 6.3.2
1. Download stock firmware 6.3.2 (latest KFU will get it for you)
2. Copy stock firmware to internal storage on Kindle Fire (boot up Kindle Fire and plug into your computer)
3. Download TWRP 18.104.22.168 from here
. (thanks sd_shadow).
4. Download latest FFF using KFU
5. Put TWRP and FFF into a folder on your computer that contains fastboot.exe
6. Make a factory cable (google "make Motorola factory usb cable") or you can buy a premade one or an adapter. Here's
7. Turn off your Kindle fire and unplug it from your computer.
8. Plug one end or your factory cable into your computer.
9. Open a windows command prompt from the folder with fastboot.exe in it.
10. While the Kindle Fire is turned off, plug in the other end of your factory cable into the Kindle fire. This should throw the KF into fastboot mode.
If you have created the factory cable correctly you should see the red Kindle screen but it should stay there and you should get a new driver install notification in Windows. Install the driver for the Kindle Fire bootloader.
11. From your Windows command prompt run these commands (substituting the names for whatever your TWRP and FFF files are called)
fastboot -i 0x1949 flash recovery twrp.img
fastboot -i 0x1949 flash bootloader fff.bin
fastboot -i 0x1949 oem idme bootmode 4000
fastboot -i 0x1949 reboot
Now you should see the FireFireFire blue screen and you can push the power button to boot into TWRP. From TWRP you can wipe everything and install the 6.3.2 file you placed on the Kindle Fire earlier (if you want to flash a KitKat ROM like CM11 or others then you must re flash recovery with latest TWRP from here
). After you are using 6.3.2 you can run latest KFU and it will work just fine.