The new Redsn0w 0.9.8 b3 supports jailbreak for iOS 4.3.4 on the following iDevices:
But for jailbreaking iPad 2 using iOS 4.3.4, you’ll have to wait for a while. Also, this is tethered jailbreak but Dev Team said that untethered 4.3.4 jailbreak might also be released soon.
Also it is recommended not to upgrade to iOS 4.3.4 from iOS 4.3.3 so you might want to stay with iOS 4.3.3 jailbroken version. If you want to jailbreak your iOS 4.3.3, then use JailbreakMe 3.0 instead of other tools like Redsn0w, Sn0wbreeze and Pwange Tool as said by @MuscleNerd on Twitter.
But somehow, if you have iOS 4.3.4 and want to jailbreak it, here’s how to jailbreak your iOS 4.3.4 running on iPhone, iPad or iPod Touch.
GO HERE, which is the Redsn0w jailbreaking process for iOS 5. The process for jailbreaking iOS 4.3.4 is also same as this. Only difference is that you should use iOS 4.3.4 IPSW firmware file and your device should be running iOS 4.3.4. And you should use the below suitable versions of Redsn0w.
Below are the download link for Redsn0w 0.9.8 b3 jailbreak for iOS 4.3.4: