Lower FPS than Vanilla in certain areas and mods

In Vanilla I can walk through the part of Old Ebonheart and get about 30 fps, but with Openmw on the same settings, it stays around 10. I also notice similar problems in Port Telvannis, Skyrim Home of The Nords, and Province cyrodiil. It is worst in Karthwasten though. If I enter the city through the main entrance by the stables and continue straight on the main road. I get 1-2 fps until i enter an interior and come back out which fixes it for a short time.

(RM-3887 from redmine: created on 2017-05-31 by Luke D, , closed on 2017-05-31 by nobody, duplicates #3355 (closed))