I am trying to get a list of all items in the players inventory with a specific tag. My thought process is that I need to loop through the Inventory using for(ItemStack a : pInv.items), and then maybe checking tags using a.getTag().equals(tag), but that seems like it might not work, and I don't want to corrupt my instance or something. Can someone tell me if I am on the right track, and if not what I'm doing wrong?

ItemStack#getTag returns a CompoundTag so if you call equals with TagKey it will always returns false (your IDE should give you a warning)
use ItemStack#is instead