if your sled rolls upside down and their is nothing preventing the oil from going back into the turbo you are going to get oil into the intake and exhaust turbine houseings. I built my own turbo system for my xp and it has done this from day one ever since I built it with a brand new garrett turbo. I didn't build any thing into the tank to prevent the oil from going back up into the turbo when I roll it. So when I roll it some oil gets past the seals and into the intake. then you get oil inside the turbo, pipeing, etc.. As long as it does not sit upside down for a long time it is not bad. I am trying to think of something so it does not do it any more and is not to much of a hassle to build or may buy a oil tank from someone else.
It is the same way on my turbo street bikes. the turbo has to be above the engine oil level. my turbo street/drag bikes sit really low. where the turbo is located for the bike to be the lowest and have tire clearance is not much above the engine oil level. I put one in a buddys trailer that has the hole cut out in the floor for the wheel chock. When we got to sacramento it had oil dumping out of the turbo inlet. Turbo was good. Just the seals do not hold oil. Others have to make sure not to put too much oil in their engine so it does not leak out the turbo. Don't ask me how it works, but they will leak oil even on a new turbo.
My oil reservoir does have a vented cap with a check valve in it. Motorcycles have a vented crankcase. I wonder if the cap was not vented if the oil would not leak past the seals. oil can't leak out if it doesn't have a place to suck air in to displace the leaking oil. hmm....
I thought the tank would have to be vented. I guess it does not because the oil going out of the bottom of the tank to the pump is displaced by the oil droping back in the tank from the turbo. Might have to try putting a cap on it that is not vented. I have a hobs switch that turns a red led light on if I do not have oil presure to the turbo. This would let me know if I have problems runing with a non vented cap.