Limp mode at 100mph p0234 (overboost)

My 110 non pd Leon keeps going into limp mode at exactly 100mph, it is absolutely fine untill then. This didn't start happening untill I upgraded the injectors to 150p764 nozzles , the car was running fine before that, the car has also been mapped this was done prior to the injectors, this was done by previous owner so I don't know if the remap is any good. I have had the car to a turbo specialist, they vac tested it and had it on the computer and couldn't understand what was wrong with it, they said that the timing was slightly out and that the vnt is sticking a small bit, they believe that the turbo would need a rebuild, but they did not inspect the turbo just from what they seen on the computer, I dont want to spend the money they quoted me, so I tried the Mr muscle method to try unstick the vanes, this has had no real effect on the car. There is also a really loud whistle noise which comes from the car which increases with rpm, sounds to me like vacuum leak, but apparently the vac all seemed normal according to the tests which the turbo people did. Can anyone please help with this as I am just about ready to give up and sell the car.

The whistle sounds like a boost leak. Hose it down with soapy water and see if you get bubbles. Getting the vnt to unstick is kind of a hit or miss problem. The only sure way to get it unstuck is to replace it. Also, maybe just only go 99mph

I had to change the injectors back to standard on the car because the smoke was too much, the car now seems to have stopped overboosting, as i got it well over 100mph, so my question still remains, why should bigger injector nozzles have caused limp mode, could it have been the map, I would like to know as at some stage I'm hoping to put them back in at some point, would it have been the fact that I'm running a standard turbo?

Turbos work off expanding heat in the exhaust. Bigger injectors will cause more heat. Tune couldn't manage it, might have been a tune/hardware mismatch.