Unpopular opinion: burning the garlic first is the real mistake, not the heat
Everyone in my family blames the pan or the flame when a stir fry goes bitter, but I add garlic in the last 30 seconds now and it stopped happening. My sister still drops it in cold oil at the start, then wonders why the whole wok tastes burnt by minute two. Which camp are you in, garlic early for flavor or garlic late to save the dish?
Man, your sister is me five years ago. Here's the fix that ended the burnt garlic problem for good: grate or microplane the garlic instead of chopping it, then stir it into the oil off the heat or right at the end. Bigger chunks sit in the hot oil and scorch on the outside while the inside is still raw, and thin garlic cooks through in seconds. Also keep a splash of water or soy sauce ready to kill the pan temp the second it goes in. Garlic early can work, but only if you treat it like a ten second job, not a base layer like onions.