Yes, better aero will help, especially with a low powered engine. However, at a track day, you don't need to overtake anyone as it's not a race. The primary purpose of a track day is to have fun driving a car quickly. Going 3mph faster at the end of the straight won't help with this, in my opinion.
The original poster referred to hillclimbs and sprints. Some of these mods will put him in a class that competes with cars that are simply leagues ahead. Define your targets and you can hit them. If you design a solution before you define its criteria, you will miss the target. I speak from bitter experience.
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