Did you resolve this issue?
I finally realized that my 2000 XJ occasionally runs poorly under load. 98% of the time, it runs great under load, but every once in a while when I put it under load it has no power and will miss if I put more throttle into it. No issue at idle though. It seems to happen not on a momentary basis, but instead, the poor running will last for minutes at a time. So far, it seems totally random for when it will happen. It doesn't correlate to engine temperature or outside temperature.
I haven't looked in detail at the injector wiring yet, but the motor mounts are in near-perfect condition. Coil pack is a new NGK installed last summer. Plugs are Bosch double iridium installed last summer. I gapped them a bit on the larger side, but the miss issue is not consistent, so I don't think this is a spark plug issue. O2 sensors are new NTK installed last summer. CPS is NAPA supreme or whatever their better model is. I tend to feel like it could be the CPS because so many people have issues with non-OEM CPS.