Paul,
That fantastic article has for some time now had THE place of honor in my D-jet file, and that's where I should have gone and followed the links to get to the answer to my initial question. My problem in dealing with the mixture issue through the MPS is that I have, as yet, not been able to remove the full stop screw/plug, even after I totally disassembled my sacrificial sensor. No amount of heat, short of melting the whole gizmo, could make it budge. I don't want to drill blindly into to one I have in the car a) because I don't want to damage the thing and b) because I'd want to adjust the full stop plug also to do a proper job. (Quite a few drilled ones with the epoxy in place in my favorite junkyard.) But the whole thing is sort of academic now because I pulled the plugs again, and now they don't show any evidence of richness. I'll just live with the lousy mileage, if I can't improve it with timing and valve adjustment. Thanks again.
Bob S.