Dirt 3 i believe is a 3.60 encryption game... here is a section from the tutorial you referred to in your post.
Q) I'm seeing almost everybody talking about a 3.6x Spoofer and the likes. What does it actually do?
A) Many people get confused on the actual use of a spoofer. What it does is, it makes your PS3 'think' that it is on the latest firmware and so prevents any updates that nowadays most games come up with. It does NOT automatically enable us to play new games, since they are ENCRYPTED with 3.60 keys, which we currently don't have access to currently. BUT, this spoofer, when used in conjunction with a debug/retail update signed with the 3.55 keys, it can allow certain games to be played (example inFamous 2, etc.)