So i have a Air from mid2011, i always just updated to OSX 10.8 and to 10.9 now. Somehow i feel that all the tweeks and apps i have installed do have a negative effect on my battery life and overall performance. Since fresh 100% clean reinstalls of iOS on my iPhone always helped me out, i thought it would be the same for my Macbook Air. Can someone recommend a good guide to put a fresh install of 10.9 on my Air? IMPORTANT INFOS: I have a Time Capsule with daily backups hooked up to my Air. And i have to tell you, i do not want to loose ANY data on my MBA....there are really important documents from university on it.