I did the same when I replaced mine.
I'm not sure when the year was that Chrysler started doing the NVH (noise, vibration, harshness) stuff to the 4.0L, but those are the only year XJ's that I want to own anymore. Going from my 88 Renix 4.0L to my 01XJ 4.0L is like night and day. One feels like a tank and the other feels, well, normal.
oh man, the newer XJs are just so much more refined in many ways, the 97+ ac blows better, the 96+ engine bay isn't a cluster @#$% of wiring and vacuum hoses, the serpentine belt adjuster actually makes sense, is simple, and works great. And I love the distributor less ignition of the 00+