Performance of my 3D design in Microstation

Hello,

I have created a 3D design of a power plant using Microstation. I imported some 3D files from other formats as well. My question is how do I improve my open/ load time of the 3d model? I have tried removing references, clearing buffers and compressing as well. I still do not see much improvements. Any Ideas on improving my load/ open time of the design? 

Thank you.