First View and Repeat View has same result for IE7 and IE8

Hi, I just setup my private instance. When I test intuit.com, I found out the result for my IE9 and FF is matching the webpagetest.org result, where the repeat view is much faster than the first view.

But for IE8 and IE7, the repeat view result is almost same as the first view result. I wonder is there any setting I need to adjust either on the browser or on the tool itself? So that my private instance has matching result in comparison to the Webpagetest.org?

Thanks

Alex