What is causing this knocking noist from the engin as you press the gas paddle

Sounds like engine trouble to me. I assume you've checked the oil level and condition and thery're good. Get to a Lexus or Toyota specialist for diagnosis. Here's a directory link for you; https://repairpal.com/lexus-repair-in-canyon-country-california

It could be engine related but could it be an exhaust leak, pinging due to bad gasoline? It is best to get this checked out as soon as possible as more damage can occur if not attended too. These are usually a very strong engine.