I have uploaded a couple of Volvo factory manual pages to #5939's photo album documenting aspects of PRV history: NONLAMBD.JPG -- From a 1979 B28F engine manual. Note that Lambda Sond is not yet part of the CI system, even on North American imports. SCREWS.JPG -- From a 1983 B28F engine Manual. The brass balancing screws are specifically referred to as "shearhead type" and the manual instructs to tighten until they snap off. AUXAIRV.JPG -- Annotated. Before CIS, PRV's used an auxilliary air valve, mounted in the same location as an idle speed motor, for fast idle. My DeLo's aux air valve is from a BMW 530: functionally the same but different design, mounted to driver's pontoon for easier access to the ignition distributor and spark plug #4. Hope people find these interesting... Bill Robertson #5939