power drop when under load ZD30

My Zd30 ddti is suddenly loosing power, then returning after a second or two. When it occurs:
Under load, usually about or above 3000rpm
When exiting a roundabout
After turning left i straighten up & it dies, a cloud of white / grey smoke appears then power comes back
Foot to floor while driving straight it kicks & splutters a little about 3700 up.
What I've done already:
Tested MAF sender-pass
Tested boost sender-pass
Emptied catch can
Checked vac hoses are not pinching & are long enough etc
Checked elec sender lines etc
Zip tied both butterflies in manifold open position
Changed vac lines & sealed intercooler as it had a slight leak.had a better response but not fixed
Dawes valve adjusted to 15psi
Vac lines checked & replaced with better lines
Swapped vac line with better vac source.
Rattle/buzzing from engine but not sure what it is.
Vac pump maybe???
What's the "hg spec for this?
It's pi$$!ng me off!
I'll drain my fuel filter tomorrow but can't see this causing all this.
Any ideas?

My patrol had a buzzing sound and was losing power under load, double check the bolts on the egr to make sure they are not loose.. Also check hasn't blown a gasket out.. The buzzing could be boost pressure escaping under load.. I found a bolt completely missing on mine.. New bolt and gasket and problem solved

Fletcha

It does it more turning left quickly, such as exiting a roundabout. On & off in a straight line.

Best be checking ic hoses for splits and seated properly
tighten all connections check your boost line

check your engine mounts as well might be pulling things
out of killter

Check the hoses mainly on the boost side as suggested white/grey smoke doesnt sound good , my exhaust just split right behind the turbo, but only made noise like blow off valve.
can't see how turning left would make it happen,?

Sounds like the famous ZD30 hand grenade problem.

Does it happen every time you drive your car? I think I may have a product that can help you with this and if your car plays up everytime you drive it I can arrange for Dave at ASE/HPD to fit one up for you to see if it fixes the problem (free of charge).

Cheers,
Adam

Good in straight line mostly now. Dies in the a$$ when turning right, then straightening up.
No probs going left.
Fitted new MAF @ $180. No change.
Drained fuel filter. No water.
Replaced & reconnected butterflies, boost & vac lines, except boost line as it has Dawes fitted.
Connected T piece to vac actuator & another vac source. Still dies but boost hits 17psi. Disconnected again.
Checked egr piping, bolts etc & tight.
Wondering if threedogs' problem with turbo splitting is mine also. Guess the heat shield is comin off.
Dieselsmart- I'm in for free a freebee!! Yippee!
I'll happily wack a sticker on my rig to advertise if u can fix this problem.

Dieselsmart - Adam.
Please drop me your details @ clieneman@yahoo.com.au
Currently in the process of removing the turbo heat shroud.
If its a 6.6 duramax ill be there shortly. Lolz

Well turbo flange checked. All sealed & bolts nice & tight.
Vac pump checked. All good unless its getting intermitent oil supply?
Engine mounts maybe a little soft but are in tact when trying to rock the crap out of the engine.
Egr, hoses & flanges etc I can see with torch look & feel tight.
Want to put a vac gauge in vac line, then see what results I get
Short of pulling things down, I'm starting to really struggle for anything else.
Dodgy Dawes valve????

I had what sounds like exactly the same problem a few months ago, only it started after transferring fuel from the sub tank. I had all the fuel drained, replaced the filter and put new fuel in. That completely fixed the problem. If the filter's been clogged with crap, then draining it won't help. Certainly wouldn't hurt to replace it and the fuel given everything else you've tried.