I own 4 XJ's, 90', 94', 96', 00'. The 90' RENIX runs stronger than any of the HO's. All of them are 4.0, AW4 3.55 blah blah blah(except the 96', its 4.10). I like the ease of troubleshooting with the RENIX also, all you need is a volt/ohm meter and the RENIX FSM. There are some advantages to any of the 3 major types(RENIX, OBD 1/2) but all in all the XJ is just a great little vehicle no matter which one you settle with.