[Alpine TSi]

How much oil? If it isn't a whole lot and is coating the inside of the pipe, it is just the build up from the valve cover vent that is routing excess crankcase pressure(and junk) back into your intake pipe, then going through the whole system too. Also gums up your IC pretty good too. That is if you even have this vent anymore, most just spit it out to the ground instead of recircing it, I use a catch can for it then dump it when it gets full(which hasn't happened to me yet even with all the blowby I get).