I have a 12/1999 108 Cdi 80 HP front wheel right hand drive Vito van. . The turbo has become noisey , and when on the open road and I get over 2500 rpm the turbo cuts out. Then if the revs go under 2400 the turbo cuts in again only to cut out if I exceed 2400rpm. Around town I can get up to 3000rpm and its noisey but doesn't cut out, but once it has cut out it continues to until the engine is turned off. Any ideas - Butch