VAG 12555 fault

Looking for your expertise, I own a S3 8P 2008 manual. High rpm are slow 5000 and up. feel it more on 3rd gear. VAG fault is 12555 low fuel pressure, I have changed both fuel pumps in the tank and the high fuel pressure pump at front. fuel filter, also new high pressure sensor, all genuine parts from Audi dealer. After all keep same fault code. Any ideas what else to do? Thanks