Those who have upgraded their Apache 2 CF servers to CF7 may have noticed that CGI.REQUEST_URI no longer contains the original request URL and query string when Apache does a 404 redirect to a CF page. For example, we just found this the hard way. In 6.1, the var would contain the original URL and the query string - it now contains the 404's URL and no query string info.
Well, there are other CGI vars available that do the trick: CGI.REDIRECT_URL and CGI.REDIRECT_QUERY_STRING. These contain all the original info on the request so you can get back to the way things worked before the upgrade.