Does it have a return (meaning two fuel lines at the rail) fuel line?
If so; strange, you got a 97 with the 96 system. If not; it's a fuel pressure dampener sitting right there, smooths out the fluctuations from injector pulsing.
check for fuel dampener and similar listings, I'm sure you'll find success...
oh, and it's awesome that you have a later year 2.5 XJ, they're super hard to find!