From what I have learned and experienced, its the crankcase filter, located (facing the engine) on the lefthand side of the rear of the rocker cover. Excessive Crankcase pressure pushes the oil thru the filter and into the inlet manifold, thru the crossover/charge pipe, out the d/v, and into the intercooler. Best bets is to remove all the above and give them a good clean and replace the filter. Cheap as chips to replace.