Some people said I9000ZSJPG consume good battery. Let's try. Because some modem handle good wifi and 3G connection. Previously I'm using XXJVR that come with the stock.
Download modem here
1. Copy "Modem_ZSJPG-CWM3.zip" to your SD card folder "mnt/sdcard"
2. Reboot recovery
3. Select Install ZIP file
Note: Usually I'm clearing Dalvik and Cache after that. Just to make sure I'm clean. but do NOT factory reset
ZS is letter code for China and Hong Kong
XX: Austria, Belgium, France, Germany, Hungary, Italy, Spain, United Kingdom