*If it happens with BOTH a hot engine and a cold engine, I'd suspect a leaky fuel injector
*If it only happens with a HOT engine, then "heat soak" is a possibility; not uncommon especially on the 00-01 XJ.
Without data, all you have is an OPINION!
Past Jeeps: '49 ******, '81 Scrambler, '88 Comanche
Current Jeep: 1999 XJ Sport, bone stock, daily driver.
I work on Jeeps!!