K&N Air Intakes and Effects on Engines

Need advice on the disadvantages (if any) of buying a truck w/ an installed K&N air intake on a 2008 Tacoma. I've read a lot of threads from owners that back the improved airflow of the K&N intake and others that would not spend the money on it when it's enclosed in the engine. What about buying a used truck where it already exists? Will it reduce the life of a high mileage engine?

 

Welcome, I bet you could trade someone for it.

 

Thanks, fletch aka. Yeah, I would not keep the K&N. When I'm in the truck on the phone, the last thing I want is more engine noise. Do you think a filter in the engine bay would be exposed to more contaminants than sucking in air from the wheel well?