I know my question is sort of answered in this post, where @Dean-Brundage answers that adding extract late will incease hop utilizaiton, and in this post, where @mdma answers that John Palmer and Jamil Z. believe that hop utilization is a function of dissolved solids in the wort.
So my question is: if I add all of my extract late (last 15 minutes), will steeping specialty grains provide enough dissolved solids to eliminate or substantially reduce any affect that late extract addition will have on hop utilization? This is a very dark porter recipe, where just the speciality grains gave a very dark brown color, to give an idea of the amount of specialty grains involved.
I brewed an extract kit whose recipe called for extract at the beginning of the boil. However, I deviated by adding the extract in the last 15 minutes. I am wondering if my beer is going to be much hoppier than planned by the recipe designer, and if so by how much.
Edit: substantially re-wrote my question to be more clear.