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Several years ago we switched from Google search to Pico Search, the paid version. I also added domain masking, one time fee, for the search results to show as search.yourdomain.com. It is customizable to add your own search button, make the search results page match the rest of your site, add tweaks to the searches and so on. Their tech support has been excellent reaching a live person on the phone who answered my questions quickly, but I've only used it 2-3 times.

Hey Alex, Sorry that you're having that issue with Keyword Difficulty! These new in-site results do seem to have thrown off our tools, so we need to consider how to address them. Obviously, in-site links take up a lot of real estate in the SERPs, so the fact that they're there does add a lot of competition. However, I'm not sure if we've decided yet how we're going to treat them in the KWD tool, so stay tuned for that. Also, if you could send an email to help@seomoz.org with your PRO email address, the KWD search you're doing, and the example SERP, we'll take a look for you ASAP. Thanks Alex!