Is major class more important than GPA?

I would like to apply to University of Illinois at Urbana–Champaign. I have checked prepscholar.com and it shows that the average GPA in that University is 3.83. I would be able to get that GPA if I take ap psychology this junior year, but my major is engineering, and I have only taken three classes that are related to my major (if ignore the math courses). Should I take regular computer science to increase my major courses, or should I take ap psychology to increase my GPA?