public class LeadJetpack extends ItemArmor implements IEnergyContainerItem {

    public EnergyStorage storage = new EnergyStorage(100000);

    ModelLeadJetpack pack;


    public LeadJetpack(ArmorMaterial materialIn, int renderIndexIn, EntityEquipmentSlot equipmentSlotIn) {
        super(materialIn, renderIndexIn, equipmentSlotIn);
        this.setCreativeTab(TechExpansion.TechExpansion);
        this.setMaxStackSize(1);
        this.setUnlocalizedName("lead_jetpack");
    }

    @SideOnly(Side.CLIENT)
    public net.minecraft.client.model.ModelBiped getArmorModel(EntityLivingBase entityLiving, ItemStack itemStack, EntityEquipmentSlot armorSlot, net.minecraft.client.model.ModelBiped _default)
    {
        return ModelLeadJetpack.INSTANCE;
    }

    @Nullable
    @Override
    public String getArmorTexture(ItemStack stack, Entity entity, EntityEquipmentSlot slot, String type) {
        return super.getArmorTexture(stack, entity, slot, type);
    }

    @Override
    public void onArmorTick(World world, EntityPlayer player, ItemStack itemStack) {
        if(KeybindHandler.keybind.isKeyDown() && storage.getEnergyStored() > 200) {
            storage.setEnergyStored(storage.getEnergyStored() - 50);
            player.addVelocity(0, 0.1, 0);
            player.fallDistance = 0;
        }
        super.onArmorTick(world, player, itemStack);
    }

    @Override
    public int receiveEnergy(ItemStack container, int maxReceive, boolean simulate) {
        return storage.receiveEnergy(maxReceive, simulate);
    }

    @Override
    public int extractEnergy(ItemStack container, int maxExtract, boolean simulate) {
        return 0;
    }

    @Override
    public int getEnergyStored(ItemStack container) {
        return storage.getEnergyStored();
    }

    @Override
    public int getMaxEnergyStored(ItemStack container) {
        return storage.getMaxEnergyStored();
    }

    @Nullable
    @Override
    public ICapabilityProvider initCapabilities(ItemStack stack, @Nullable NBTTagCompound nbt) {
        return super.initCapabilities(stack, nbt);
    }
}

I think you will want to create a new one and then in the methods you need to call the super if it doesn't match yours. IE

@Override
public ICapabilityProvider initCapabilities(ItemStack stack, NBTTagCompound nbt) {
	ICapabilityProvider superProvider = super.initCapabilities(stack, nbt);
	return new ICapabilityProvider() {

		@Override
		public boolean hasCapability(Capability<?> capability, EnumFacing facing) {
			return capability == yourCapability ? true : superProvider.hasCapability(capability, facing);
		}

		@Override
		public <T> T getCapability(Capability<T> capability, EnumFacing facing) {
			return capability == yourCapability ? yourCapability : superProvider.getCapability(capability, facing);
		}
	};
}

I don't see how you could incorporate facing into an Item, but...ehh.

yourCapability? do i have to create my own capability? and if so how?

yourCapability? do i have to create my own capability? and if so how?

Yes you will have to create your own capability. The forge documentation is a little low, but there are examples out there Choonster has some example on his github. There is also this which helped me understand what I need for a capability specifically.

https://github.com/Choonster?tab=repositories

http://www.planetminecraft.com/blog/forge-tutorial-capability-system/

All right, ill check em out, ty