2006 A4 lost power on the road
 

I was driving down the road the car all of a sudden lost power. Took it to the mechanic, pulled the fuel filter, it was quite plugged. I have error codes 08851 fuel regulator valve and 00135 low fuel pressure. We checked the in tank and mechanical fuel pumps pressures and they are within spec. The car runs better after fuel filter R&R but codes keep coming back if I accelerate. Not sure what to do and I do not want to R&R fuel pumps unless I have to since they cost a pretty penny. Any suggestions?
Jaime