We here at PSI understand that many of our products are bought and sold on the secondhand/ used market. Like most race components our supercharges have a limited service life. While many of our blowers are still in service after 20+ years, this life span of components is determined by many factors including: operating temp, amount/frequency of backfires, ingestion of debris and importantly maintenance (or lack there of) etc. If you are considering purchasing a used PSI screw supercharger that has been recently re-certified  we STRONGLY advise you to request the seller to share the screw supercharger inspection report so you the buyer know exactly what you are buying(please note that any new superchargers on their original SFI certification will not have an inspection report). It has been brought to our attention that some customers will send in a supercharger for recertification or repair and do the minimum work required to meet the SFI certification and leave potentially costly repairs for the buyer to learn about after the supercharger is sold. PSI can not provide information about a customers personal property without authorization.