I wish that I could tell you for certain, Ed, a lot of those mods take place gradually during refits and overhauls. You'll see guys working on some project or other and assume that all they are doing is some structural work and the next time you look there is just a plain ol' solid piece of steel, then other times you'll go back and there'll be some weird looking dohickey sticking out where nothing should be at all. I remember a fast attack in drydock with, what looked like, a large form fitting billboard on the starboard side. We do all of the work on this particular boat but nobody could remember it being fitted up on the hull. It turned out that it was a passive side scanning sonar array that was being tested for the Virginia boats being developed at the time. It was removed during that drydocking. Also, during that same drydock availability, stern ACLs (Accoustic Countermeasures Launchers) were mounted.
As to your question, I think that the changes were being implemented after 1999. But I don't know for certain and I don't know much of what goes on at Puget Sound Naval Shipyard