If I'm not mistaken, is has to do with nandrolone sides. You can get things like gyno that is caused by progesterone and not estrogen, in which case no amount of AI will help you. They are both extremely suppressive, and the two work just as synergisticly (is that a word) against you as they do for you. Some people run them together w/o problem, but for the most part it is a good idea to leave them seperate. Run something like EQ or Primo in place of the deca and I think you would be a much happier camper.