SYE is not required for the 4 inch. But is recommend, anything higher it becomes required.
Do not go with your cheaper kits!
These kits will supply your lower links but not the top Links (or vise versa) which is when ur pinon angles will differ with a 4 inch. Which makes for caster and other steering issues.
Weather the lift includes shocks or not shouldn't matter. It just let's you choose the shocks you want so don't let that be your deciding factor.
I would recommend you spend the money and get a kit that includes both upper and lower control arms.
While your at it get the SYE and the cv stile rear drive line. You will NOT have to touch the front drive line.
The cv stile rear drive line will eliminate any vibrations that you may get other wise.. spend the money, the ride quality will be well worth it.
If you do a lift that includes upper and lower links, the SYE and the cv stile rear drive line you will have no pinon angle issues,
:Theory of a dog:
If you can't eat it or screw It, piss on it and walk away!
!Just Empty Every Pocket!