I have a 2013 Burstner IXEO on a Fiat Ducato Chassis with a 2297cc diesel engine. Just lately it has become sluggish in acceleration. On motorways it gets up to speed (70) fine but on hills it slows down markedly and becomes slow exiting from junctions / roundabouts. Any thoughts. The vehicle is maintained by a fiat / motorhome specialist. it has 18,000 on the clock. It has had problems with the Particulate filter in the past but this has always come up in the fault log. No faults are shown and none are pending.