2012 Maytag air conditioner. Rechecked everything on system again. Ran system for 10 minutes without a filter and let it stabilize. Put in customer filtrete filter and found it causing an airflow restriction dropping the pressures. Customer has been using these filters for several years. House is 27 years old and has never had the ducts cleaned. Customer mentioned pulling small pieces of drywall debris from a couple of his registers. If a large amount of dirt and debris has built up in ductwork this could be causing a sever restriction on airflow and with the filter as well. Recommend them to fresh air Corp for a duct cleaning and to use less restrictive filters. Merv 8 or less. Delta t is currently at 18 degrees. All okay at this time.