Yeah, it's the VANOS which needs to be replaced (I recommend DrVanos.com
once you find which one you have). It's a frequent thing unless you get the reengineered ones at Dr. Vanos. It's safe to drive on as I have been doing it this whole time. It may mess with timing which might make some cylinders misfire but it hasn't done that to me but once. The only thing it affects is your engine performance and gas mileage. I plan on getting it done sometime soon I just haven't had the time or money to do it.