Arrived at location on 7/14/22 - Met Nick at truck. He said the shelf is getting very hot. Turn on. The flames are rolling back and not flueing properly. Checked the burners and burner tubes. They were sooted up. Cleaned soot from both the burners and tubes. Gas pressure at 10”. Lit pilot. Stays lit. T urn on burners. No flames are going through the tubes ok. Shelf still hot but not as before. He verified operation and said it was much better. Back in service.