My D2 is seems to be spitting oil out of the stack onto the top of my cat. The Cat has been stored for some time and someone else told me it could be from idling for too long of periods, however, it doesn't seem to be improving. Any thoughts.

Best hope is to work it hot and hard to help burn it away and possibly keep it gone for a while.

If you can't get it stopped, make sure it is getting up to operating temperature (check thermostats) and all the injectors are spraying properly.

No joy there, you might possibly try the BonAmi treatment. A small dose of the powdered limestone in the intake will cause temporary accelerated wear and possibly (re)seat the rings.

Long term solution is to re ring and hone or replace sleeves. Then you have to get the new ones properly seated through the same "work it hot and hard" treatment.

I let my D2 idle over lunch once. When I came back, there was oil spots all over the hood and ozzing down the stack. I decided that idling was not a good thing to do.
I now only use it to work, pushing brush, pulling loads like dead trucks or actual dozing. No more oil problems.
Work it good and hard as above suggestion. Also, I was pulling a dead 2-ton dodge with no wheels mounted, out in the pasture, was a real good load and no color to exhaust.
Try a good workout first before getting too clever.
Eric

Thanks guys, I'll give it a good workout and see if it helps.

It could be wetstacking from not being worked hard enough. If you have a leaking injector, that will also create the problem. Listen to it and see if you can hear it skipping any.