Don't use synthetic in the primary.
Well, that's what I recommend.
I use formula plus. It can be found at any Harley dealer. I know, I hate those places too but to me it's a necessary evil.
I put synthetic in my primary ONCE. I didn't like the way it felt. Was as if the clutch was slipping, probably what you're describing as a power loss.
Anyway, try switching your primary fluid and let us know what you think.
I ride my bike HARD. And I felt a big difference between synthetic and formula plus.
Others might suggest amsoil or another non Harley fluid but I stick to what I know. And I know formula plus works real well for me in the primary. Also, I can take a quick ride to my local HD, make fun of the chromos, and have my fluid within 30min of leaving the house.
Go with what you want but as an experienced Bueller I say stay away from synthetic in the clutch/primary.