Noticed I was starting to get really, really low FPS in my park. I went to the 'lowest' graphics settings and had no performance increase. I removed a bunch of the scenery stuff that I had downloaded off the workshop thinking that might be the problem, specifically things that had billions of lights and effects, but only saw a very slight increase. So I decided to close my park and see how much FPS i had with no guests, and viola I was back up to reasonable FPS numbers. Turns out guests will murder your FPS and I highly recommend setting a guest limit before you start hacking off sections of your park.