Silver club fall tune up on 2018 American Standard 90% gas furnace in basement. Spoke with customer and he would like to purchase a filter. Inspected system and it has same issues as noted before, extra debris is getting into the return side and under the blower wheel. The system is low on return air which is causing it to short cycle. Vacuumed out accessible debris as a courtesy and changed 24x24 filter. Checked blower, heat exchanger from below, capacitors and burner compartment. Cycled system on and checked gas pressure, replacing gas cap, electrical and heat rise. System is working within manufacturer specifications with the fresh filter. Recommend changing filter monthly. Also noting previous recommendations for cleaning plenum properly, capping flue, air duct cleaning and increasing return air that are attached to account. Bill filter to account per office manager approval.