Audi a4 1.9tdi avf 2004
For the past couple of months the car has been sluggish performance/economy wise.
Today while driving at steady 50 i decided to put my foot down but got no response.
Checked for codes and the following came up:

17957 control valve boost pressure - n75 open circuit / short with ground

17994/ Engine Mount Solenoid Valves (N144/N145): Short to Plus

18027 glow plug relay (j52) open or short to ground

17932/ Fuel Pump Relay (J17): Open or Short to Ground

The n75 valve and the fuel pump relay where replaced less than 3 weeks ago.
Why would the glow plug relay fault come on when the vehicle is running?