I've noticed, that this plastic device (not sure what it is?) pictured below is very oily and damp on the bottom, and there is a black pool of fluid sitting below it on the head of the engine (maybe a few ml's worth, looks like oil?)

Could this be related?
Again, the issue is that if I go half throttle, audibly let the turbo spin up, and then go full throttle, it pulls perfectly. But if I jump straight on the throttle quickly, theres no torque or power at all.
Many thanks