Hi guys, I have a 3GS that was replaced by Apple.

The thing is, what I've found, after doing some extensive research is that the model and the serial number are vital to knowing whether you have an old bootrom, or a new bootrom.

I've found that if your model starts with MB, it is the older bootrom. It is also the older bootrom if your iPhone was sold before the 40th week.

I'm a bit confused about this because I have a MB model, 09 is the 4th and 5th digits of my serial number.

Normally, this SHOULD mean, is that I have an old bootrom 3GS, if I'm not mistaken.

The issue here, however, is that my 3GS was a replacement phone. The serial number ends in FW3NP, which I have never seen before (first time ever replacing any of my past iPhones). I also had issues with using sn0wbreeze 1.5.1, which supposedly worked with old bootroms but not with new bootroms, and was unable to jailbreak with it.

Can anyone tell me if the same rules apply? I was looking forward to using OS4. Please reply soon, thanks in advance.