Jurupa Valley ductwork work splits across the older Mira Loma/Glen Avon and newer Sunnyslope/Pedley housing-stock divide. Older Mira Loma and Glen Avon homes from the 1960s-1980s commonly have undersized return ducts and degraded insulation — original ducts were sized for the equipment of the era and the insulation has deteriorated over 40-50 years. Return-duct upsize is the typical fix. Sunnyslope and Pedley newer subdivisions usually have R-6 to R-8 insulated flex that mostly holds up — sealing failures at supply boots are the typical issue. Static pressure measurement on every diagnostic confirms whether ducts are the actual issue.