Cadillac STS-V Series Forum Discussion, K&N finally releases air filter for STS-V in Cadillac V-Series Forums; Is the K&N that much better than the stock filter? I read somewhere that the stock system was pretty good ...
I came across quite a few articles on K&N air filters vs OEM (or any other dry paper filter). Although it seems almost subjective, there tends to be the belief that K&N does have better airflow, but lets more particulate pass through; while typical paper filters are a bit more restrictive on the air flow, but do a better job of stopping dirt.
That is a high level synopsis of the research I have came across. Read through some of the articles and judge what you feel is best for you and your car.
I emailed K&N a couple weeks ago when this thread was posted and this is the response I got.
Currently K&N only performs and lists Dyno sheets for our intake systems. We do not perform or post Dyno sheets for replacement air filters. however because a K&N filter is less restrictive than the stock filter, it can provide an increase of between 1 and 4 horsepower. Results will vary depending on your vehicle, driving habits, load on the engine, existing air system restriction, and other factors.
If you have any additional questions, please feel free to contact our customer support department at 1-(800)-858-3333.