Ford Transit Year of construction 2006 TDCI 280 85

Good evening, have 2 questions: 1. How can I change the two wedges at my father’s transit? Have looked at this a little bit and with the little one there is no tensioner to see and with the big one already. However, you wouldn’t get the wedge belt by if you took it off because the tensioner sits directly in front of it. Must the tensioner down? 2. The vehicle had a fault in the AGR and air mass meter. AGR replaced air mass meter with brake cleaner cleaned. The vehicle runs Sporad As I said, sporadically and not always. However, if you speed up and keep the speed at approx. 2000 revolutions it runs quite normal, it is only in idle. I only renewed AGR and did not learn anything. I have also renewed fuel filters. If you had an idea what it could be? It would help me very much. Thank you in advance MFG