Seat Leon 1p 1.4 TSI, error P0299?

Hello, I've been having a boost pressure problem with my Seat Leon 1p for some time now. Sometimes it loses power at all and goes into limp mode, especially when I drive up a hill on the highway. It always says it has boost pressure issues. I've already replaced all the sensors, but that didn't help. What's bothering me is that oil is leaking from somewhere around the turbocharger. If anyone knows what the problem is and how I can fix it, I would be very grateful.