@Pumpa:
You should
always do backups before you overwrite something.
Always. As you have probably noticed, that will save you from a lot of troubles.
Anyway, the procedure to backup the diags partition on the PW2 is exactly the same as on the previous models: perform a dd dump of the /dev/mmcblk0p2 partition. To backup the diags kernel, run
geekmaster's getkernels script.
If you only overwrote the diags
partition, but not the kernel, then you can use the image
here (that's npoland's dump). If you also overwrote the kernel, then you're out of luck, or have to ask someone with a PW2 to provide it to you.