hhave you got a crappy cvh oil cap still? had a similiar prob with mine, changed that for a oil cap for one that you lock in using an alan key not had it since and make sure you dip stick isnt loose like the other fella said its an air leak.
be careful of taking the dump valve off when I ask about this a few months ago, few people said they took theyre dump off and they blew the turbo within the week,