I'm not sure what IFWI refers to. I thought it's only about the host firmware (i.e. the BIOS region of the flash). Make sure the other regions are restored as well. If you have an image of the factory firmware (not a backup), I'd try to flash that.
IFWI - Integrated Firmware Image
It's the complete flash image that includes the descriptor, ME firmware, BIOS/bootloader, etc.
The FW can theoretically damage the hardware, but it's unlikely. If you haven't tried that yet, I'd remove the CMOS battery, too. Some registers are powered by it and could still hold a value set by core- boot/FSP. A warning, though, I've encountered one board where this made things worse (but the board survived).
Tried removing the battery earlier. No help.