Please help! Overboosting 1.9tdi 110

Hello all, I have a 1.9tdi 110 golf which I believe is a non pd ASV engine?
Basically, when I hit 3k revs in 4th and 5th (mainly) I lose boost and get limp mode. The turbo boosts really well when under 3k with no strange noises etc.
I have tried the usual, checked the boost solenoid, checks for vacuum leaks, ran fuel additives, even tried a mr muscle clean, but there hasn’t even been a slight improvement, so is there anything else I should be looking at before I go and buy a new turbo? And are all turbos a direct fit? (Can I put a pd130 straight on)
Thanks in advance for any help!
Adam

It is a VEP TDI. Have you done a code read on it.

Yes I’ve got the code
P1557, charge pressure control: positive deviation

That code is one of the most common you would ever see and earlier versions are nearly older than the internet itself.

17965 (P1557) - Charge Pressure Control: Positive Deviation

In the vast majority of cases this will be due to sticking vanes inside the turbo and to deal with this the turbo will need to be removed and have the exhaust side bead blasted to remove the hard carbon. Using oven cleaner will not remove the hard carbon and as it is water based it can cause corrosion damage to the turbine shaft and its piston ring and this can suddenly fail and pour engine oil into the exhaust system.

Oh okay, I did think that was the only real fix just wanted to make sure before going out and purchasing a turbo/getting mine remanufactured, thanks a lot for your help buddy!

Hello, I was wondering if you’d be able to advise me on a turbo im looking at, Ive found a turbo that is for an AJM engine, the guy reckons it’s a 110, but I’m pretty sure it’s a 115 engine? Would this turbo be a direct fit?