I own a 1990 SC 5 spd for 25 years. 75K miles, car used on weekends only. This winter car kept outside. There is a fairly loud mooing noise (much like a cow) when first started up. Noise is only at idle and goes away after car warms up. Car is completely stock and has never had any repairs or issues. Could this be the supercharge equipment needing servicing ? It sounds louder when listening near air intake.