Loss Power at 2000rpm

[Cognac50]

Well Hi guys

I’m new here & am DESPERATE for HELLLLP!

Ok here we go I apologise in advance for the way in which I am describing my issue as I honestly don’t have a clue about what is wrong. Also it is loooong winded story.

Car:

2008 Patrol wagon
Manual
2” Lift Kit & Longranger 145L fuel tank
Common Rail Turbo Diesel

Has a 2011 3.0L CRD engine with 126,000kms


Future Ventures:

4 x ARB BP-51 Shock Absorbers
Itech Dual Lithium Battery set up
Raslaar Dual Wheel Carrier
Runva 11xp Winch
Bush Company 270 max awning
4 x Stedi Quad Pro Driving Lights on roof
Stedi Type X Pro Driving Lights
Stedi LED H4 Headlight upgrade
Stedi 40.5” Curved Lightbar
Stedi 22” Lightbar
Dyno Tuning Ultimate Diesel Tuning


History:

Seller told me (so yes I knew it had an issue) that the engine had been replaced with a 2011 3.0L CRD engine with 126,000kms on it & that when he drove it it was surging & they lived on a quarter million acre property & needed something reliable so was selling it.
Negotiations started paid $7,000 instead of the $11,500 he wanted.
Got to Coffs Harbour and low & behold it was surging. Took it to mechanic they fixed surging issue ( so I no longer Kangaroo hop down the road).
Car has sat in the same parking space since 12 December 2021 & I was told it now lacks power. Picked it up yesterday as don’t have the money atm to fix it.

Whilst driving home I decided to go up a hill & it crawled up it at 40kms when I drove on the Highway it hit 2000rpm & lost power (My Grandmother could move faster than me & she’s been dead for 30 years :-)
Once I backed off & accelerated again it was fine until 2000rpm again.

Everything on the engine is from that 2011 engine nothing has been removed.
Previous owners changed Oil, Water, brake, power steering, gear fluids, all the injectors are new, new MAFs, new Fuel & Oil Filter, new hoses to intercooler & filters.
My uncle checked out the wastey thingy it opens fine.

The only thing that isn’t in from the 2011 engine is the ECU. When he put that in it wouldn’t start period. The old engine ECU is back in & working.

Any help would be appreciated please. So far it has cost me $300 a mechanics & $1800 to transport it from Darwin & a lot of stress.

I love my new truck & just want to go camping 🏕 with the Grandkids.

TIA