Speeding up Windows Server

I have a completely standard test Xenforo forum installation with only 40k posts running on a dedicated Windows 2008 server running PHP on FastCGI. The server has to be Windows due to another application on there.

The load time for each Xenforo forum page is between 1.5 and 2 seconds for me. (About 0.25 to 0.5 seconds slower than this site).

I have the same forum running live in vBulletin 3.8 and load times are maybe 0.5 seconds in total. So Xenforo feels very slow by comparison. The vBulletin is a bit optimised for speed with jQuery turned off.

Is it normal for Xenforo to be 4 times slower than an optimised vBulletin 3? If not does anyone have any ideas how to speed Xenforo up a bit on a Windows server or what diagnostics I could be doing?