I can't really take credit for this, but I just restored my IMEI without a backup of the efs folder. Keep in mind that I actually deleted my efs folder by accident, so I didn't even have the original efs folder.
The original thread I referenced is here:
http://xdaforums.com/showthread.php?p=31771228#post31771228
FYI, this method will restore your phone to stock Gingerbread.
Here is what you do:
1.)
A) Download and unzip the Gingerbread unbrick package here from (
http://xdaforums.com/showthread.php?p=27286083#post27286083):
w/ root -
http://d-h.st/ewu
w/o root -
http://d-h.st/G6g
B)
Download and unzip the efs zip here:
http://xdaforums.com/attachment.php?attachmentid=1152914&d=1340558510
2.) Place phone in download mode.
3.) If needed, install latest Samsung USB drivers by installing Samsung Kies from HERE.
4.) Open the included Odin exe.
5.) If phone is detected, the window under ID:COM will turn yellow.
6.) Click on "PIT" to browse to and select infuse_gb.pit. Make sure that Re-Partition is selected.
7.) Click on "PDA" to browse to and select PDA_UCLB3.tar.md5.
8.) Click on "PHONE" to browse to and select PHONE_UCLB3.tar.md5.
9.) Click on "CSC" to browse to the efs.tar
10.) Click the Phone EFS Clear checkbox
11.) Click on "Start", and allow Odin to flash the phone. Do not unplug or power off the phone until Odin is finished.
12.) When the Odin dialogue reads "PASS!", the phone should reboot into the stock UCLB3 Setup Wizard. For me this step just proceeded to install an update and the reboot the phone.
Once the phone reboots, if your SIM card is installed you should be good to go, otherwise you will get an alert about your SIM card which means you need to power off and pop in the SIM card.
Thanks to the original thread author for this one.