Dumb question here, and maybe you've already addressed it and I missed it, but...
Did you have the front end alignment checked?
I realize the ZJ springs likely only raised the front around an inch, but I'd think that could still be enough to cause issues with the alignment. It seems shims helped, but maybe its a compund issue. It's probably worth getting on an alignment rack to at least check it. Most places won't charge for a check if the alignment isn't needed.