Carried out seasonal AC maintenance on a Trane XR14, model 4TTR4048L1000A. Identified compromised ducting that was reducing system efficiency. Repaired the ductwork by sealing leaks and replacing sections with significant wear using UL 181 tape and mastic. Additionally, installed new insulated flex duct, model Thermaflex M-KC, to ensure optimal airflow. Concluded by testing the system to guarantee restored efficiency and comfort levels.