C30 2.0d power loss when accelerating
 

Hello, and apologies in advance if this question has already been asked and answered, had a look and can't find anything.
So, I have a 2007 C30 2.0d, had it for about 4 years, it's my baby, wants for nothing! Has 156000miles, and recently have had a couple of engine issues. At the moment if I'm accelerating (fairly hard maybe) it'll just suddenly dip in power, throw up an 'engine system service required' warning and then the power comes back. The egr is currently unplugged (has been for months as it failed) and just changed the boost solenoid valve and MAP sensor has also been changed. I've got a bad feeling it's turbo issues, so hoping someone has advice on what to try before me spending £1200 on a new turbo!!