I just installed the K&N intake kit. I have a few questions?

1. I can feel a slight power improvement at low rpm, but nothing at high rpms.
2. I have a definite louder air intake noise. I checked all the fittings and no loose connections. Above 3K rpm, I have a slight whistling noise? Is this normal?
3. I removed the positive and negative battery terminals prior to install.
4. I still have a slight hesitation-stutter at higher rpm’s, I was hoping this install would alleviate that problem, also.
5. I have not gained any improvement on my MPG's?

What do you think?

Thanks

Rick