How do you take these off, are they double sided tape or screws?

Bolts you have to take off the sound guard on the inside of the hood & they are right there.

krazzycowgirl is right. A bit of caution though. The louvers have plastic studs that protrude through the hood. They are attached by stamped lock nuts. Take care when removing! The studs are VERY prone to breaking off...

Break more than 3 or 4 on one loover and you might lose them at highway speeds Ask me how I know

Those plastic studs become very brittle after 10-15 years, be careful!