I used to be able to determine the search engine used for highlight/right click searching by selecting from the drop down menu in the search box. Whichever was the active search engine was the right click search engine. Firefox 34 only allows the default engine for right click. This is awful, it is one of the most important features to me in Firefox, depending on what I was searching for I often switched between various engines. Why the decision to reduce usability? I probably will go back to Opera if this function isn't re-instated.

BTW, never in a million years will I use Yahoo. i made a habit of deleting it from my list of search engines, it always had a sort of National Enquirer feel about it. I also made a point of ignoring Yahoo Answers if they came up in a query. The amount of wrong information was stunning.