Why to which?

I have also run K&N filters on cars, but only after other extensive changes in the engine. Porting, polishing, carburetor changes, camshaft, headers and complete exhaust. Otherwise it's a waste of money. I've never run one on an otherwise stock engine, because there is no gain. It's simply a waste of money.

Why would I shy away from a street car running a K&N? It says something about a driver, if he thinks a few extra (phantom) horsepower is needed in his car. It also makes me wonder what other useless devices he's tried.