Yep. I didn't even know CA had its own emission guidelines when I was looking to buy, though I wasn't surprised in the least to find out. That said the jeep is otherwise in great condition, so some extra hassle over the cat now doesn't bother me in the long run.

My only question about putting a non-CARB cat in is would the on board computer accept it as 'good enough' to stop throwing the low efficiency code? I honestly have no idea if they're smart enough to tell the difference, though again, with California regulations, it wouldn't surprise me if they were.

 

From everything I read on an XJ they aren't sensitive enough to know the difference. The pre-cats aren't all that dense anyway (almost like a screen) and odds are the non-CARB ones aren't much if any different physically, they just didn't go through the additional testing and red-tape to get CARB approval.


On a side note PA adopted California emissions for new vehicles starting in 2008 (many other states including MD, NJ, NY, MA, RI, CT, and VT have also recently adopted California-emissions standards for new vehicles) so if you ever buy a new vehicle in PA or buy a 2008+ used vehicle that was originally sold in PA it will have California compliant emissions components. However unlike California PA has no restrictions on importing a non-California emissions new vehicle, so you could go to another state that doesn't have California emissions buy a new vehicle and bring it back to PA, but for most people that isn't worth the effort.

 

Looks like for now the question is moot. My mechanic reset the code and was able to get the required number of miles on the engine without it tripping, so the current system as it stands was able to pass emissions. (Over the last year or so the code got thrown pretty regularly and hung there for a few weeks at a time; in the last few months though it's been on constantly, so I thought it wasn't going to pass this time). As of now the CEL is still off, but it'll probably return in a few weeks or so.
Thanks for all the info; I'm pretty sure I'll be re-reading it come next inspection.