There were reports from iPhone Dev Team member Musclenerd about the release of a new downgrade option in redsn0w for 06.15.00 baseband in iPhone 3G and 3GS. They have launched this new version of redsnow named ‘redsn0w  0.9.14b1′ a few moments before, which will help you to downgrade your baseband from 06.15.00 to 05.13.04.