Loss of Boost with TD4

Good Afternoon All.

I am having some troubles with my ’03 TD4 Freelander.

In a nutshell….. I loose boost.

When I am accelerating up through the gears it is fine. She pulls like a train.
The problem occurs when I reach aprox 70/80 mph (I live on the Isle of Man so no national speedlimit)
She looses power, not completely but I am 90% is is a loss of boost.
What I have found is that, if I flick the ignition off and back on again I get my power back. (until I try and accelerate again)
This problem is amplified when I am towing.

I have done a few things to try and alleviate the is problem but to no avail.
I am running a Rover Ron Synergy 2 Box with a new Pierburgh MAF sensor.
I have mucked out the EGR Valve, which was coaked with about 8mm of crap.
I have also changed the vacuum pipe running down to the turbo.

These changes have turned it into a bit of an animal with a bucket load of torque, but, she still looses power.

Has anyone ever experiences this before?

I am not a mechanic, more of a tinkerer (more on my V8 Lightweight) so I am stumped now.
My only possible thought is that it could be the waste gate sticking, so when it starts to overboost and the waste gate opens upon acceleration it is, sometimes sticking open?
(I am not that clued up on waste gates unfortunately)

Thankyou for your assistance with this.

when did you last change your fuel filter? they are known to cause poor performance issues. remember there's a strainer in the tank too.
also fuel pumps are a common failure, if it's on its way out it's poor delivery rate will give similar symptoms.

haven't heard of that many turbo's giving trouble so eliminate fuel starvation first.

Pretty much where I'm at , thought it was ok after the fuel filter was changed but came back , next try the fuel pump .

atvb Paul.

This happened to me after I had been playing on Salisbury Plain. The guys on the run helped me and as well as checking for split inlet hose we had the Air filter out. None of this worked and RAC man couldnt find anything wrong fault code wise (even though the warning light came on) The problem sorted itself out in the end but I think that the tuning module I had fitted may have gotten damp and taken a "funny turn" until it dried out. Maybe disconnecting the RR module and checking for power loss.I think turning ignition off then on, clears a safety mode in the ECU.