Review on K&N Cold Air Intake Kit for Toyota 4Runner V6 4.0L (2010-2019) - High Performance, Boost Horsepower: Model 63-9034 by Patrick Burns

I don't know why K&N decided to make this air intake suck air from the engine compartment. If they wanted to highlight a nice filter, they could cover it with clear plexiglass. It gives you more flow, but if you ever ride your 4runner through the mud you'll see why that's not a good idea. The entire engine bay is covered in dirt, which means you're covering the intake with dirt that gets sucked into the engine. Not to mention that the air in the engine compartment is hot, resulting in lower air density and therefore less oxygen. The factory air intake has an opening that draws outside air through an opening in the passenger side fender. I haven't even installed it. just got back I will look at the TRD air intake which has a higher flow rate but takes air from where the Toyota should. Added to this is the claimed increase in horsepower. misleading as it does not indicate if the engine was warmed up and does not list exhaust characteristics. The back pressure from the restricted exhaust manifolds, combined with the MAF reading, is guaranteed to shut down the ECU and prevent any power gain.