For performance tuning, check this section of the documentation: https://wpdreams.gitbooks.io/ajax-search-pro-documentation/content/performance/fine_tuning_the_search_configuration.html
I highly recommend steps 1.1, 1.2 and 2.1
You can also check the ajax performance tracker, to see what the 'Average request runtime' is: https://wpdreams.gitbooks.io/ajax-search-pro-documentation/content/performance/ajax_performance_tracker.html
If the request runtime on that page is much lower than the actual response, then the ajax request is probably affected by a 3rd party plugin/script.
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