i'm confused......why do you have a 2003 XJ Cherokee? Do you mean a 2003 WJ Grand Cherokee? Also look into the NGK plugs. I think they are around the same price as the E3's crashcraddock suggested. I'd suggest investing in some good wires like NGK or Bosch, etc. They will resist more frequency. In cheap wires the radio waves from other electrical components such as the radio can interfere with the wires causing hesitation, missfire, etc.
1998 ZJ Laredo, 4.0L, 2WD, it's boring