I arrived and discussed issue with the customers. I found the furnace in a roll out switch fault. I reset the rollout switch and tested the system. I checked and confirmed furnace flue pipe. I did adjust the gas pressure down slightly for high stage. This is a L.P. Furnace , I set the high stage to 10 in w.c. . The safety did not trip while on site today and I did not see any signs of flame roll out. I cycled the furnace and checked the sequence of operation. The blower motor and inducer motors are operating with in specifications at this time.I discussed our maintenance plans with the customer. The system is currently heating correctly.