what voltage are you vaping at?
Usually 8W. I bumped it up to 10W when I was drinking. I'd tried it at 12W briefly when I first got it, but still, that's only 6W per coil (5V, 2.1 ohms, new SVD, single 18650, 70%PG)
I just looked at a replaced coil head from an iClear 30 that I had been using for 2 months. The plastic on mine were not burnt like yours. Perhaps you are dry burning for too long of pulses or at too high of a voltage. I've never had any burnt taste from any of my four iClear 30's.
I would think I did that dry burning too, and some of it may be, except that it had a bad taste from the start, even after rinsing it with hot water. The taste got better after several days use but still had a slight burnt smell that lingered in the air after using it even though I couldn't taste it anymore.
Here's an iClear 16 head. I don't have another 30 head but As far as I can tell, they're the same except for the wicks.
One of the top coil plastic pieces is actually touching the bottom coil. The other is only 1/2mm away judging by the wick slot in the head which is 1.5mm. I looked at another head and it's about the same.
I've thought before that fasttech may sell brand rejects that don't pass inspection but are still functional, but using plastic anywhere near the coil is unacceptable to me, might as well be smoking.
I was able to push the plastic down a little with a needle to get it away from the coil, but I still don't think I'll be using my new iClear 30 or three iClear 16's unless I can rebuild the heads myself or at least remove the plastic, which I expect to be difficult.