a mate got a 2.8 voyager on a 55 plate it will not rev over 2.5 k and got a loud whistle coming from the engine if it is the turbo will a 2.5 crd turbo fit

 

You may have a boost leak check your pipework. Are you getting black smoke.

 

no black smoke

 

So turbo is working then but its getting curtailed. Check vac hose to actuator unit. But still sounds like boost leak if you have any left. Once heard someone saying the turbo is operating correctly if it whistles. An HST power car Whistles when its powering out a station due to noise coming out exhaust box. Whistle noise is caused by Turbo blades going through sound barrier...So the end answer is you have an HST Valenta engine and turbo under your bonnet...May I ask you how you fitted it.