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Our company plan to use in our product page a live chat support app. But  I concern about the page load time. The script is loading asynchronous and in the inner tests increase the average page load time with around one sec. Previously the load time was between 2.5-3.3 sec after the chat support increased to 3.8-5 sec, but sometimes there was extreme +10 sec worse results. My question is how much can this impact to our search engine rankings?