Replaced flame sensor, heat shield and heat shield gaskets, and fresh air fuel plenum under warranty. Increased blower fan speed From medium low to medium high. Tested temperature rise with is 40 degrees and within range. The heat shield warped due to the factory gas pressure being set to high. The gaskets and hoses were replaced not because they were needed but because they part of the area that failed and should be replaced to keep the system in like new condition. Air flow was increased to provide more flow to the downstairs. Along with this adjustment the ducts were inspected and are properly attached and routed. Found 3 registers partially closed upstairs and opened these supply vents. During the heating season it is not recommended to close any supply air registers. System is operating properly at this time.