Hi, here is the firmware of Ecoo E04 Plus 3GB.
Firmware: Ecoo E04 Plus MTK6752 Android 4.4 3GB 16GB Firmware
Passcode: geekbuying.com
These are the Tutorial guides:
Tutorial for the whole process of flashing ROM
Firmware update by USB wire Tutorial
Tutorial and download for SPFT Driver installation
Have a nice day!