A transfer case lowering kit may eliminate the vibes, but an SYE is the best fix with a longer drive shaft. It is not overly difficult to install on your own. Advanced Adapters sells some high quality kits with detailed easy to follow instructions. If you have the mechanical know how to remove and reinstall the transfer case, then you should be good enough to install the kit. It seems much more intimidating than it really is.
Oh yeah, check your rear pinion angle also. Since installing your lift, it may be at a bad angle.