I don't get how the BBD stepup piston is supposed to work. Vacuum holds it down and a spring pushes it up when vacuum is low, but there are plastic tabs on the accelerator pump rod that force it to move up at down according to throttle position. So how can the vacuum and spring control anything if it's seemingly slaved to the throttle? Or do the tabs give it enough wiggle room to allow vacuum and spring to control it within a small range?
I adjusted the stepup piston screw. I believe that adjustment caused it to run richer at speed now (AFR is about 12-13 at part throttle). However, now it's also rich at idle even with the idle mixture screws all the way in. I also had to back the idle speed screw all the way off to make it idle low enough.
Also, I have a couple of vacuum lines capped off, and the caps blow off when I shut down the engine. Also the engine diesels sometimes after shutdown.