Here's another update in my saga: my XJ ran great for about a week and then she died on the freeway today with the same symptoms as the first time my CPS died: bucking, stalling, erratic idle, then dead. Towed it back to the house. Interestingly, once she cooled down I was able to start her right back up and drive her into the garage. I replaced the exhaust manifold with a new APN exhaust manifold. Total time was a little over 4 hours to swap it out.
The old exhaust manifold had a huge crack that went almost all the way around the pipe. I'm thinking that I was killing CPS's so often because the exhaust gasses were flowing right onto them and killing them. Anyway, the removal and install sucked (the bottom row of bolts is a complete bitch) but I got it done. She is much quieter now, seems to have a lot more power, and hopefully I can stop bumping this stupid thread.