Thanks guys,
Everet, if I'm not mistaking you have a 4dr Sportage (as most of you have, at least according to the pics), while mine is a 2dr.
Because of the shorter wheelbase, the drive-shaft is shorter too, and that makes the angel between the drive-shaft and the diff bigger than in your cars (it's like you do a 5" lift).
My lugnuts are torqued properly and the vibrations started after the lift.
I guess that when the front will be lifted as well, the angel will drop a bit but I'm starting to re-think this lift and maybe to settle with just 1-1.5" spacers.
I'll try to take some pics and send them to you in the next couple of days.
What about the transfercase drop, did someone do it before?
Thanks again!