Injector Insulators/Grommets - What causes this wear?
 

So pulled off my primary injectors on my FD3S to swap them with a modded stock rail with 850cc secondaries and I found the injector insulators/lower grommets absolutely stuffed.

Attachment 751397

They are only about 1 year old and in that time have done 3000km and 3 track days. The old ones I pulled out 1 year ago didn't look like this at all. They were broken a bit worn, but not falling apart and melted like these are.

Any ideas what can cause this sort of issue?