Upon arrival checked the HVAC system for a reported weird noise coming from the unit in the basement. Found the new installed HVAC system making a whistling sound due to opened gap in the return air duct to the gas furnace. Repaired the issue, unit is on line at this time. NOTE: A home service VIP maintenance contract is STRONGLY RECOMMENDED, Ms. Katrena said her husband will have to decide. And will call to sign for.