Thank you kris,
I have already checked the boost line and banjo bolt and they are both very clean all the way to the switchover valve on the firewall and down to the engine.
One new thing ive found is that the EGR valve on the valve cover leaks a lot of oil into the air filter which leaks directly down into the turbo. There's a metal tube which connects into the underside of the air filter housing and i think it's meant to redirect oil, however it does not attach to anything, it only ends near the oil pan. I think its meant to drain into the pan but im not sure.