trafic van no power under 2500 rpm?

hi ,went to my van this morning and went to start it when it jus cut out ,tried this twice more then stated but once it started there was no power on the accelerater for bout ten mins .after that would revs only to 2500 revs .when past that would shoot of like turbo kicking in any help as to no clue why its doing it many thnks ....