Is 2.65 available? If not, can you place the item in a separate category and hide the cat?
Delete item from Gradebook
We ended up doing a combinations of things to solve this--we were able to create a category, hid the category and give the category a value of zero for those items we didnt want in the total grade at all. I didnt solve all of our problems since it still appears in our student information system (external to Moodle) which causes some confusion. We created other categories and adjusted the value of the category relative to the course total to adjust scores from there.