I am experiencing the similar problem with my 01. Just went to deals gap and on the way back going down the hills in gear decelerating it starts to smoke. Once I get on the throttle again it stops. Not sure what the cause may be but I have a venting to atmosphere set up on both ports in the valve cover. Could not really find a good answer searching so if there is another thread related to this issue sorry for repost.
Could it be the turbo not being able to drain under this condition?
The car runs fine under normal driving conditions except down hill. Any help is appreciated.
I am thinking of installing the venting valve into the downpipe from Summit racing and running it to the catch can to draw vacuum from the down pipe.
Is there a better way?

Oil- 5w40 Rotella
Turbo Drain is pretty good simmilar to high HP miatas from this forum.
73,000 miles 20,000 turbocharged.

 

Mine was doing this becuase of a lack of oil restrictor on the oil feed for the turbo, but that's on a BB 2560R which doesn't need as much oil for the bearings like that T3 of yours does. But it could still be the seal o nthe turbo, it could be PCV, it could be blow-by. Remember that when you apply throttle, more air is going through the engine and out the exhaust..possibly diluting the burning oil. When you let off and air flow is reduce, it becomes more appearant.
The easiest things to check first are the PCV and breather. Also, with the engien running, pull the dipstick to see if any oil vapor is being pushed out the dipstick tube...which would indicate blow-by.