I see this thread is from quite a while ago, but it's great that you're thinking about your future career path. Going to a tuning school could be a fantastic choice if you have a strong mechanical background and a passion for working on cars.
While Hennessey's Tuner School is one option, you might want to explore other schools as well. Take a look at programs offered by various trade schools that specialize in automotive technology and tuning.
Since you mentioned working in HVAC, you might also want to consider furthering your education in that field.
https://www.onlytradeschools.com/hvac/ can offer you valuable skills and job opportunities.