Is #4426 concours? If not, why rebuild the engine to factory spec? I'd think you'd be happier with higher compression and/or a more aggressive cam. I'm beginning to suspect my Volvo re-engine may be a bit more pedestrian than JZD's. Does your PRV man have any references to ID just what I've got behind me? FWIW: great success so far idling off the upper air assembly bypass screws (no hunting there). May be cantankerous this winter until warmed up -- we'll see. Bill Robertson #5939