Kernel is the heart of operating system. So getting a good kernel is important. It will improve performance, better features like overclocking, battery life and so on… XDA Developer, intersectRaven compiled kernel with Mjolnir for the Amazon Kindle Fire with few optimizations. It supports ARM code optimizations and able to overclock up to 1.2 GHz. Furthermore, it is available on CM7, CM9 and stock ROM. Personally, I tested intersectRaven Kernel on CM7 ROM.
Installation guide ~ How to install update zip on Kindle Fire with TWRP 2.0? (Video)
Download intersectRaven Kernel for Kindle Fire here.