Right now, the 4" lift kit is a thing of myth... along the lines of bigfoot, unicorns, and mermaids. Some have claimed to have seen it, and there are even some blurry/low resolution pics of it, but one has not been caught in the wild!
Gaze,
I heard scientists are planning a research trip to try and prove it's existence.
They are bringing out all of the high-tech gear: radar, sonar, thermal imaging, etc.
From what I looked at under my riot while installing the lift there are a lot of things that will need to be swapped out for beefier parts if you go more than the 2 1/4 inch lift. I wouldn't trust the stock parts to withstand the stress of the angles from a higher lift.