R32 Turbo Issue ?

[Lrs94]

So I recently bought an old skyline of a friend, it was running 1 bar boost pressure (standard rb25 with bigger rear housing) and ran perfectly fine, but turbo used to blow bit of smoke while under load, so it was replaced with a standard rb25 turbo (ceramic blades) and works perfectly fine upto 0.5 bar (roughly standard boost) but anything more than that it, makes the car shudder/shake/jolt violently, like a huge flat spot, that you can not get past, I checked all my coil packs visual and measured resistance every thing was fine, checked my plugs they all looked fine checked gaps, replaced fuel filter. I don't think it is a fuel issue or exhaust blockage, because when you set boost 0.5 bar it happily revs to 7k rpm,. Going to do compression test soon.

I have search all over Internet and can't find anything, I was wondering if any one has heard of anything like this or may know the possible cause, it is hard to describe over Internet, be easier to show,

[mz.qiksky]

Is it making any noises? Whooshing really high pitched or anything like that with the shuddering of the car? Do you have a boost gauge installed, if so is the boost spiking?

Reason I ask is because my old op6 was surging, causing the car to jolt and shudder. It was set to 10psi but was spiking to 14psi and making a definitive high pitched whine/whooshing noise. If its that, its very dangerous for the turbo and engine and I would recommend dropping the boost right back to a point where it no longer does it, or getting a new turbo.

[Lrs94]

It sounds fine, to me it seems like fuel or ecu is cutting it out, like it builds up above 0.5 bar and drops back and builds up and drops and you can't get past it, but it previously was running 1 bar fine so I don't understand what could be wrong with it