Odds are that yes, it is the Daystar kit.
The ride probably seems rough for two main reasons.
#1. They put a lift on and kept the stock shocks (it's not a strut in front, it's a coilover shock). When you lift a KJ, whether with spacers or springs, you need to put longer shocks on. With spaces in the front and stock length shocks they've stretched the shock to it's limit and are also putting compression on the spring. The shocks are probably worn out because of this.
#2. The stock springs start to lose their "springyness" and sag after about 30-50k miles.
The best fix is to put swap the shocks and springs out for a well developed lift kit. Most people here will recommend the "Frankenlift" by All J Products.
http://www.boulderbars.com/frankenlift.htmIt's not really cheap, but well worth it. I've had mine on for over 70,000 miles and it still feels great, and rides much better than it ever did stock.