Toyota Repair: 94 4run V6 oil leak, valve cover gasket, side valve

Question
i'm down to last oil leak repair.  1994 toy 4runner, V6, auto, 121k MILES.  Vin# JT3VN39W2R0138379.  Oil leaking from driver side valve cover area in the rear next to fire wall.  it's a slow seeping oil leak that drips onto the exhaust manifold/tailpipe joint just as the motor warms up.  you know the smell.  i cleaned engine bay and installed new valve cover gasket (torqued correctly) and still have same leak.   i'm not a mechanic by know means but is there something else that may cause leak or is it time to pull heads off/shave/reinstall?  other than that, it runs great.   **thanks for your help**.

Answer
The only other thing I can think of is that the end plug on the head may be leaking, there is a 2 inch round plastic plug on the end of the cylinder head , they should be removed and resealed with sealer when replacing the valve cover gaskets, another possibility and not uncommon, is that the oil passage in the head has an external leak in which case the heads have be removed.