1. it could be coolant due to the color and nature of the cloud. you can sort of tell if it is by the smell coolant will have a sort of sweet smell when it gets burned. as well the cloud will seem to stay around and not disappear like exhaust will it will all most float. if you are running water mostly then it will still float just no smell. keep an eye on your coolant level.
2. it could be fuel but i would say lean not rich would explain why it seems better at throttle your ecu richens up as boost increases.
3. oil dsm's and oil seem to hate each other when in doubt it always seems to be a oil leak i dont have any good ways to tell were the oil would be coming from you can try a catch can to remove the blow by variable leaving just basically the turbo.
hope this helps my guess would be fuel tune with a little oil considering your compression numbers, try a wide band to monitor the afr's
