I imagine I am wrong, but one thing I had heard was that Poltergeist would have a few small changes in what was otherwise a copy-paste. The long Black wall corridor would be shortened in favor of more tech support, being one thing I had heard.
(Personal spec: There's also a mask made by Immortal Masks that seemed to be of a specific character from Poltergeist 2 being made, to where I wonder if that might make it's way to this house).
Can be wrong! But that is one thing I had heard a little bit back, to counter the IU mods.