used... I think it has to do with the fact that these ovens blow hot air, where as the others didn't. Also there are 4 burners, and you can regulate each one by covering the holes that the air comes out of. They can be either FULL (no holes covered), HALF (half the strip is covered) and NONE (No holes covered)... (keep in mind this is my terminology. The original configuration (Going from where the piza goes in to where it comes out) was FULL-FULL-NONE-FULL. This way, it was burning the cheese, and the crust was cooked, but white. Now it's configured FULL-NONE-NONE-FULL, and the cheese is a a bit better, but the crust is still the same. Tomorrow morning I'm gonna switch to- NONE-NONE-FULL-HALF, hopefully that'll help.... I've been in business for 20 years, so I'm not really trying to change the cheese. I use a 3 blended cheese 50% Cheddar 25% Mozzarella 25% Monterey Jack.