After the dealer put a fuel pressure sender from a Turbo Volvo onto my "Not a Turbo" 2005 V70, it made the fuel pressure sender CEL error go away, but it also did two other things. Thing 1 was the fuel pump became very loud and the noise was constant. It sounded like a coffee grinder slowly dying while grinding up gravel
The other oddity was the MPG immediately jumped about 10. I was getting about 34 and even was in the 20s full throttle climbing a hill
I bought my own Bosch fuel sender from Amazon that was the right part number - 0261230109 - and immediately both issues were solved. The fuel pump is quiet and MPG are back to the 24s. My theory is these sensors use the ubiquitous 5 volt sensors and the turbo version is calibrated differently. While the correct sensor shows 52-55 PSI, the turbo version was showing 42-44 PSI. I think the turbo sensor is calibrated for higher pressure and the 42 PSI reading really was 50 something. I think it cranked the fuel pump full blast to try and make it to 55 when it already was. I think the MPG computation must use fuel pressure as an input and thus reported less fuel being used than was the case.
Could be wrong on all that, but it seems to be logical.