oily sparkplug

my car is 96 sl2 manual tranny. just wondering why one of my sparkplug is always oily. the one near the engine mount pasenger side. i think its #1 cylinder. my engine runs fine on idle. but misfire on accelation at around 2000-3000rpm. my sparkplugs are new and gap clearance is correct. also oily on top of cylinder cover around that same sparkplug. anyone know why and how to fix the problem?

Replace the valve cover gasket. Guaranteed to fix the problem.

Replace the valve cover gasket. Guaranteed to fix the problem.

yeah sounds like valve cover leak. probably the oil fouled the spark plug, so new plugs will be needed. i will say go with ac delco rapidfires for plugs as they are the best i have used in my car and ive been through many different ones.