drop-in filters doesn't really make any difference. If you notice any difference then it's probably psychological. The only reason to use drop-ins like k&n and redline is they are re-usable and each clean can last up to 40k km. As opposed to cheap filters...only last 10-15k km.

If you really want performance, then get open pod filters. Then again, open pod filters are more expensive and gain very little power. It's more for those who want to mod their car every little bit for performance.