In Career Mode, your setup effectiveness is heavily tied to your R&D (Research and Development) Prioritize Chassis:
Save : Qualifying (low fuel, soft tires), Early Race (conservative wedge), and Late Race (loose wedge + open tape). The AI in Thunder 2003 has fixed pit strategies—you can beat them by pitting 2 laps earlier than their cycle. nascar+thunder+2003+setups+best
To maximize your top speed on straightaways, manually adjust your 4th gear until your engine reaches approximately In Career Mode, your setup effectiveness is heavily