I have been using the Samsung i9103 for quite a while and have tried out most of the available experimental ROM out there. Most of today was spent trying to find out the right combination to make the phone usable again. Here are the steps to having a really good setup on this phone

  1. First follow the guide below and install the XXKPE ROM following the guide below. You will need to use Odin to flash this ROM onto your device. I used the ROM link below the guide

Guide : http://androidadvices.com/making-galaxy-sl-i9003-xxkpe-update/4/#.UA0w8aCeaSx

ROM : http://hotfile.com/dl/145780524/f7d1f45/I9003XXKPE.zip.html

  1. Now you need to root the device and can use the following guide and image to do the same. It worked out pretty well for me.

Guide : http://forum.xda-developers.com/showthread.php?t=1191623

ROM : http://coveringandroid.com/wp-content/uploads/2012/01/I9003XXKPE_RootingPackage.zip 

  1. Open the Tweaks application and apply the various optimizations. In addition to that install AWD launcher! Its an absolutely phenomenal launcher imho,

Other tuneups you can do are

Shift to Ext4, read the post below on XDA developers.