Didjoo try freezing it? The way it goes is like this I think, you put it into a ziplock, then squeeze out the air. Pop it into the freezer, & wait a couple hours, then take it out & try removing it.
For future reference, it is better to take the hsf out with a twisting motion, rather than a straight pull. It is harder with th P4s so a few back and forth twists to start will help.
You are about to answer a thread that has been inactive for more than 6 months. If you still wish to proceed, please ensure that your posting is original and does not duplicate or overlap any prior responses to this thread.