I bought a used iPhone 3g and unlocked it for tmobile. However I noticed that my battery is no that great. Which battery should I get. I know 3g iPhone comes with a stock 1100 mah battery, but I have seen some batteries with 1600 mah rating. Which would u recommend, stock or 1600 mah battery? Also how do I get my google callendar to sync with my iPhone sock callendar app?