1998 740il: P0170 fault code

My "service engine soon" light just lit this past week. The obd readout says P0170 (Fuel trim Bank 1). From this forum and others the most probable reason is leaky intake manifold or PCV valve. I cannot find any repair manual for this vehicle. Can anyone point me to a diagnosis procedure for this problem to narrow it down between the two. Obviously I don't want to yank the intake if I don't have to.

Also where is the PCV value on this car anyway?

Thanks