Webb

Hi all I recently purchased a 2002 c5 2.2hdi but seems to have a few issues.The esp/asr fault keeps appearing when accelerating to about 60/70mph also the anti pollution fault appears at the same time and the car goes into limp mode. I was told it was a issue on the air intake side so I replaced the air mass flow sensor and air filter also cleaned the egr valve with spray, unfortunately none of these has helped does anyone have any advise as it would very much appreciated.