Arrived and discussed issue with customer. Customer stated the system felt like it was not keeping up last night correctly. I checked over the system and checked thermostat temps calibration. The thermostat is reading the correct temperature.the unit kept and maintained 76 degrees while on site today. The system cycled on and off correctly. I did. Find and replaced two dirty 20x20x1 filters. I also checked temperature rise across the unit. This system is a dual stage furnace wired up single stage. The furnace board will engage 2nd stage after the run time has reached. While in single stage it is blowing out cooler air and slower speed. This helps with efficiency of the unit but this was the only other thing noted. System is currently heating correctly at this time. I did let customer know this call has a 30 day warranty since there was not an issue with the unit satisfying the thermostat today.