Ho so i buyed audi 2012 year , has 97,000miles done . when drive longer time on road it goes limp mode . The problem comes faster if i push harder on revs . It starts all good for fist 20 min but after that when drive a car you can start hearing small pump near engine keeps working louder and louder and harder than you know that limp.mode gonna come . You have to stop car and turn off engine wait for 2or 3 min and its ok again for short time . I changed all 3 pumps in car all 4 injectors ,Regulator ,but it didnt fix problem fault code is p008700 fuel rail/ system too low .permanent. filters all changed pls help because i spend a lot money  .

Ok after alot spendings i found problem myself pump in diesel tank supplie/return lines were switched .So i switched them back and its all good again no limp mode all good . If anyone has this problem p008700 fuel rail/system pressure too low and buzzing sound in pump check this fist thing in car . 

 

 

Glad to hear you have resolved the problem Vitalijus. How did the fuel lines come to be connected wrongly in the first place?

I have no idea mate. I brought car with buzzing pump and later limp mode most likely someone before me was doing something with car changing pump or something ,and connected it wrong way around . It was crazy because in 3 places nobody could see that problem . And i managed to find it only because of other post in other forum were guy brought vw golf with buzzing pump .