If it hasn't already had the fuel pump replaced, I would look at that too. Check post #77 in the link below if you ever notice any over heating. Mine is a 2002 and these are some things I remember lots of folks talking about in the early days.
overheating issues, but only at idle
2002 Sangria Red ZX5 with ABS, Moonroof, K&N Air Charger, Borla Cat-back exhaust, Edelbrock header, Random Tech Cat, Bosal Flexpipe, Magnaflow Resonator, SVT Suspension, Auto tranny