Has anyone seen a definitive improvement in idle from changing those 9 inch spark plug wires that run from each coil on top the valve cover to the spark plug? With such a short distance, I'm wondering if degradation really happens. This is on a GM LS V-8. With long wires, cooking between engine and firewall on a transverse V-6, I would think degradation would be more prevalent. My wires are 12 years old and have 205,000 miles on them. The idle is not quite as smooth as when the truck is new. The spark plugs are only a year old. Thanks.