Losing power on acceliration

Check to make sure the breather/air filter box is sealed. You have some really bad air inlet leakage.

cute no year, no country stated then posts to usa forum.
we dont have this car. here. i think.
so are you asking how to diagnose turbo issues, on fixya
that be like asking how to do brain surgery on , Mr, PHIL
the PCM may see the boost too low for load and RPM.
so, that can be lots of things, besides a bad turbo cant spool.
even a stuck open waste gate.
or controls issues,
best is to get a complex car serviced, by someone that can work complex turbo diesels,

if serious on DIY, why not buy the book on the car
the FSM
then see the turbo section and do the tests stated there.
if that sounds hard, it is,

I am assuming you have a diesel as based on your description, the most likely cause is a split or crack in a turbo hose. You will also get black smoke if that is the cause.

Freelander TD4 diesel has a chain (mega bucks), L series diesel (pre BMW engine) has a belt (plus a small belt for the injection pump). the K series 1,8 petrol and KV6, 2.5L also have belt's.

Would really need more details on the vehicle. Petrol / diesel etc

Is the engine management light on? Are there any fault codes?

Power lose while driving is most likely to be caused by the mass air flow meter, leak at a vacuum or intake hose, turbo leak etc.

More details please........

well it runs,,,,,
low power on a diesel is
1: low compression
2: bad fueling
#2 can take forever to find, if you dont know what engine it is or what fuel system was used.. no country stated, so cant guess
read the wiki on land cruiser and see what you have.
we dont know.

series 80?
series 100,200 ??? what?

• 4.5 L 1FZ-FE I6 gas
  
• 4.7 L 2UZ-FE V8 gas
  
• 4.2 L 1HZ I6 diesel
• 4.2 L 1HD-T I6 turbo diesel
• 4.2 L 1HD-FTE I6 turbo diesel
• 4.5 L 1VD-FTV V8 turbodiesel

one of those last 4? engines?
once there, we try to find out how it works. each varies.
can fix engines with out knowing exactly what it is, and the injection system, used.
cant.

diesel pump might not be working right. Try and check fuel pressure. I dont know if its turbo but if the turbo is failing then you will loose power

I don't wish to worry you but I think the turbo kicks in at around 2500rpm and it sounds like it isn't doing so, hence the management light coming on. It could be that failing. Be careful here, apparently the turbo uses the engine oil to maintain its operating temperature and if the turbo seals fail in anyway it eats the engine oil, with the resulting total failure of the power unit. So if you do nothing else, keep an eye on the engine oil level. (You may also notice oil smoke out the exhaust as well).
Unfortunately it looks like a trip to the dealer for them to check what the engine management is saying.

you can fit a new engine and gearbox but i dont think another type engine will fit the gearbox

Although fuel pump is about a year old this could be source of your problem.