[ROM][AOSP][24-Feb] Slim ICS [2.7] - 70 MB- Clean, Simple & Fast - The Google Way - xda-developers
2.7 is out.
Basically such roms are packing kernels which have additional tweaks available like CPU overclocking and all that crap. You can ask in the thread about people which kernel are they using.
However, currently known kernel is "Devil's BLN supported Kernel". The version 14.2 to be specific. People are reporting the later versions to be not-so-good.
[Kernel][ICS] Devil 1.1 [12/02/12]-BLN-Touchwake-USB_Host-LiveOC-BFS-DeepIdle2 - xda-developers
However flash at your own risk because changing Kernel MIGHT create more problems for you. So better to do a Clean Wipe with every kernel flash, just to eliminate the possibility of any issues.