Oil smell through vents

[stealth 96]

its a 96 jetta 2.0 liter. 104,000 miles. Everything runs fine....im gettin 28-30 MPG and its smooth. Its just that after i get off the highway and stop at a light or suntin......there is a heavy smell of oil that comes from the vents. as soon as i begin to move again the smell goes away and there is no sign of it...its just when i come to a stop after goin for a little while. What is goin on here and what can i do about it? Thanks guys

[boschmann]

It could be oil coming from the valve cover gasket dripping onto the exhaust manifold.