Dont need the metal part to use pod.
Finally I rewicked the pod. It's actually quite easy and done in no time. I burnt off the gunk of the coil with a windproof lighter. That worked very well. Wicking was easy too. The inner diameter of the pre-installed coil is exactly 2mm.
The only thing I did wrong was not to take out the rubber chimney. After I put the bottom of the pod with the coil and cotton back into the pod, the chimney didn't seal the tank properly. That resulted in flooding the tank and leaking trough the air hole at the bottom of the pod. So, pull out the rubber chimney, slide it in the base and put back all together into the pod. Perfect.
I didn't put back the metal part. As you said, It's not needed. However, I will keep then.
Thanks guys for your help. I'm sure this will help others too.