Hello,
I think there`s a bug in quick search form at as you can see at http://auto.demoflynax.com/ if you search only for Make/Model and ANY subcategory: results shows ALL listing. And if you choose the same option in Refine search in the left - it`s working. After some research I think the problem is in action="http://auto.demoflynax.com/index.php?page=autos&search-results on the homepage and action="http://auto.demoflynax.com/index.php?page=autos&search-results" on the search page. I can confirm that the same result is showing at my website too.

Please be advised if I`m not wrong.