Esp/asr parking brake and cruise control problem

Hi, I am new here, well new to posting comments I have had lots of good advice on here and managed to change my own egr valve thanks to a few images also so thanks for that.
Problem is 57plate c4 picasso 1.6hdi vtr+, started juddering, jumping whilst accelerating at about 3000rpm, gradually getting worse accept now it judders and esp/asr comes on dash and it cuts out. will start straight back up and drive and might not happen for age, just starting to get more regular last few days since egr change. Also if accelerating in cruise control using the steering wheel controls it also sometimes has this big judder/loss of power and cuts off and can't then use cruise control until you turn off and restart the car. I have a little code reader that says egr now fine and stuff but get turbocharger underboost code thats it, if i clear it and go out and no judder, no code, if i go out and it judders and is slow to accelerate, code comes back. Is this all linked you think, thanks in advance just wondered if this is familiar as I have found lots of things on separate faults but not all together inc crusie control, wondering if just a switch or sensor causin it maybe