The 4.0 upgrade seems to have slowed my forum down and the home page (forums) takes about 4 seconds to load.  On the same server I have a 3.4.7 system and the home page load is instant so I am going to rule out network.   Any thoughts on where I can start to look?

The slow 4.0.6: http://wheelhorseforum.com
The fast 3.4.7: http://myoldmachine.com

The 4.0.6 is significantly larger which would lead me to some sql parameter.

http://community.invisionpower.com/files/file/7514-htaccess-for-ips-forums/ try this