Vibration only on acceleration would be the driveshaft; i.e. pinion angle is off. Assuming you have the basic ProComp 2.5" lift, this only comes with springs, shocks, and bump stop drop brackets. The JKU works very well with a simple lift. I have installed Tereflex and RE simple lifts before without issue.
Where did you measure to think you were off by 2"?
Before you start throwing money at it, verify everything is installed correctly, torqued to manufacture's specs, and get an alignment.
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08 2dr Sahara
17 Gobi Recon