Performance optimization in editor vs PIE mode

Hi guys
Another performance optimization question!
If I get acceptable performance in editor (30-50fps) but it drops to 4 or 5 fps in PIE mode, what does this suggest?
Any suggestions welcome!
Launching in 2 days.

Attaching a stat unit for both standalone and PIE mode
statUNIT_inEditor
statUNIT_inPIE

You’re drawing about twice as much stuff in play as in editor. What is that?