I've had good success flame polishing and my guess is that your torch is putting out too much heat. I use a crème brulee torch and its going to be a little more precision and less heat than that torch. Also, you have to go conservative. Slowly wave the flame over the ramp getting some of the cloudiness out and then let it get completely cool before trying again. Little by little. The main problems I've had is bubbles. That's what you get when you hold the flame over the ramp too long. The plastic starts to boil.