So brake shake upon deceleration is fairly common, but it's not normal. many times it's due to overheating of the brakes that warps the rotors. If your vehicle is still under warranty it's worth taking it into the dealership to have them check the rotors. If they've overheated they may be able to replace them under warranty. If it's outside of warranty, the good news is is that a set of pads and rotors isn't that expensive and would easily fix the problem, as long as you know that the rotors being warped are the cause. You could also potentially just turn the rotors and be good to go depending on your milage and remaining pad life.
That said you also say that the pulsating started after the lift was installed. It's not really normal to have a pulsation upon deceleration after a lift. Usually the vibrations, clunks, and bumps associated with a lift happened at almost all times after the lift. or maybe exclusively when turning to one side or the other. I would try going down the path of possible warp rotors before removing and reinstalling anything on the lift side of things. That's said it certainly wouldn't hurt to double check your work and make sure that everything is tight and looks to be holding up well after install.