Hey guys I have the same issue on a 2l v6 it stared 4 months ago and one day it just disappeared and the car was fine till I had the engine wash. I drove off car was fine got home and after 2 hours drove to shop and the problem was back I check for leaks don't hear any but the car does this hissing sound by the air box when idle and slight shudder on driving the workshops are of little help only waiting to fault find by buying parts after parts on my expense and not getting to issue any ideas of people who had the same issue.
