Obviously an oil leak will be the main problem with a bad valve cover gasket. I am wondering if it will effect the way the engine runs in any way. I know some engines will run bad when there is any kind of bad seal. A bad seal will allow air to get into engines that have negative pressure in the crank case. This effects the regulated air flowing through the PCV valve and in turn the tuning of the engine.
Does anyone know if the 2.5 L Cougar engine has any issues with a bad seal other than an oil leak?