I `m using the durable cake mix recipe(yellow ultra) mix without sour cream. My box mix says ultra should I use pudding mix,or should 1/2 box be enough pudding.

...if you omit sour cream then you're really not making the 3D Durable Cake recipe.

A lot of members add a whole (small) package of instant pudding and/or an extra egg to boxed cake mix to make it more dense.

HTH