ProComp's 4" kit needs a SYE kit and CV driveshaft just like any other 4" lift does. It also needs better riding shocks because the ES-3000 shocks that ProComp includes in that kit are the stiffest riding shocks known to mankind. They are not valved for Wranglers, they are one-valve fits all no matter what vehicle it's for. There are many better riding shocks that cost no more.
Not to mention the standard control arm that ProComp includes in that kit is so inflexible that it can tear the control arm mounts off the axles if you get on a trail that is uneven enough to really push the suspension. That's not an opinion, that is a fact that is well known with their control arms.
Having once worked for ProComp's parent company, Transamerica, I wouldn't touch one of their control arms or shock absorbers though their MX-6 is decent. Their springs are good quality, it's just the rest of their standard kit I would't touch. There are much better brands out there that are well respected. ProComp is a 'for the masses' kit that doesn't really get any respect among experienced offroaders.