There is only one current way but odds are you can't do it because it involves using a mod chip. Because the infectus chip allows you to backup your firmware and restore older backups. And you can just install an infectus chip and then ask someone for their backup because each backup is different. This is because each firmware is custom coded for each motherboard. There is speculation that there is a jigkick downgrade like psp has.
Umm when am I gonna get my quality post? Its been like 2 weeks