As an elite stairrunner aka towerracing it is all about your diet and hydration levels.
Most people eat too much fat and their blood cells clump up and find it hard to pump around the lower limbs making you feel breathless as well as your blood flow in your lungs is restricted compared to your hypothetical twin who eats under 10g of fat per day, smashes in enough sugar and drinks enough water for clear urine every 2 hours.
I absolutely dominate on the stairs. 2 at a time and grab the rail. You need good upper body power if you want to go your fastest.
We would do Baiyoke Tower II in Thailand. 80 floors. Do it every second day full gas for a month as base training.