Where is the air filter on a 1999 ES 300 Lexus?

The air filter on a 1999 Lexus ES 300 is located in a plastic housing under the hood, near the front of the engine. It's typically on the driver's side (left side in the US), but you might need to look closely as it's usually not immediately visible. You'll likely see a large rectangular or sometimes slightly oval-shaped plastic box with a few clips or screws holding it closed. Look for some kind of air intake duct connected to it.