Wont rev past 3000

[endo97531]

Hi all , I have a vito 111 cdi, that wont rev past 3000rpm , when you put your foot down it revs clean to 3000 then smokes alot , if you keep your foot down then in around 5seconds it clears revs all the way to 4,500. I was thinking a split boost pipe but it will clear if you keep foot down , I have not driven the van on the road yet as it has needed a lot of work to get it road worthy