my wp site is hosted on an IIS windows server. Issue is, my ttfb when a user is logged in is a lot longer (2/3 seconds) then when no user is logged in (super fast). See this video for a demo:

I've tried many different permutations of cache plugins/settings (W3 TC and WP Super Cache) and iis settings, and I don't think it's down to that. Also, the amber warnings through Query Monitor are only a matter of miliseconds. I disabled any user manager plugins for this demo of the problem.

I have tried disabling the 'do not use cache for logged in users' for both cache plugins, but this didn't seem to make any difference.

I'm just really curios about the difference. I can't figure why the loading times are so disparate depending on whether a user is logged on or not....

Any ideas?