IMO the biggest difference is in the ECU's (ECM's). There is a lot more support today to tune the 04-06 models while support for the 02-03's is being worked on. By tuning I mean making changes in the A/F maps, the ignition timing maps, rev limiter, speed limiter, fuel injector tweaking, etc. This can be done by flashing the 04-06 ECU ROM, while the 02-03 models must rely on piggy-back computers with limited tuning capability.
hey im new here, i just have a quite question.. i want a spec v but is there any different between the 02-03 and 04-06...plezzz let me know...