As Usual Apple closes it's signature verification for iPhone for Restoring below 4.3 because it will always close old firmware verification whenever new version will come.
So People having problem has only one method to use,that is Custom firmware at the moment.
If you try to use Custom firmware without
PWN DFU you will get error
16xx,3194.
So any thread or Posts about this problem will be deleted without notification.
P.S.
Various methods to check Bootrom version of 3GS
1. Model Number of New Bootrom phones start with "MC"
2. Serial number is XXX
4XXXXXXX or XXX
0XXXXXXX
3. Handset should be in
DFU mode
Device Manager on your Windows PC.
Look for 'Universal Serial Bus (USB) Controller', you will find 'Apple Mobile Device USB Driver' as a sub item there.
Right Click and choose 'Properties', navigate to 'Details' tab and select Device Instance Path from the dropdown list.
At the end of this information string you will find the bootrom version, i.e. (iBoot-359.3.2) or up who knows
if this Method not work for you,Use
Another Method.
Another
Method to flash 3G,3GS,4 if Saurik server has SHSH for required firmware.