Thanks everyone for your replies.
I replaces the HGs less than 6k ago following the popular method on this forum. I have been checking them almost once a week since then because it was the first time I've done anything like that to a car. The HGs and all the front ende seals are new.
Getting under the car I did notice that the oil pan gasket is " weeping" a little oil. I didn't replace it with the other seals because I don't have the ability to pull the motor.
I'll keep investigating. I'm beginning to think it only smokes when I use 4wd because I'm going up steep enough of a hill for the residual oil to flow back to the exhaust.
It doesn't leave any oil on the ground when I park.
Thanks