There may be a thick spacer gasket between two thin paper ones. Check the spacer for cracks. If it needs replacing, be sure the new one is the right thickness, because this governs the fuel-pump lever stroke .

ls3 valve cover gasket. OEM gaskets are recommended for LS3 engines to ensure a perfect fit and reliable performance.
The garter spring is located at the end of the primary sealing lip and used to apply pressure to the sealing lip against the shaft. Common garter spring material types are:
Oil Seal 75x100x10 A Complete Guide