I cleaned my engine after my camsahft and timing belt change and noticed oil leaking from around the oil fill cap. I inspected the gasket and it seems to be fine and the tabs were bent to the bottom. I pulled the cap off with the engine and the was steady air blowing from the hole. Should there be some pressure or should I attribute this to blow by? The car has 154,xxx miles. Should I be concerned or is this normal wear and tear?