Limp mode

[Jewy25]

Hi hoping for some help, 2007 A4 2.0 tdi, over the Christmas I had the battery unplugged for a few days while I sourced a used alternator and fitted. When I started the car back up the eml and esp was on. I also changed the injector loom shortly after this. Only recently my turbo has been coming in very slowly and at around 3k instead of 2k ish. Then going into limp mode. This was happening intermittently. Had the codes read and was showing a few different things each time, mostly glow plugs, and steering angle sensor so I’ve just changed the plugs today (haven’t changed steering angle sensor). Car was fine and running good until I had these changed today. Any ideas? All this seems to have stemmed from when battery was unplugged.   Cheers