Manifold Vacuum Experiment

I would sswap the pump cam from the back onto the front. If you turn the 3 hole cam upside down, it will have a very close profile to what the blue cam does. You may have to slightly bend the pump lever. This has cured off idle stumbles for me several times. I can't remember which hole you use when putting it in upside down, but it will be obvious. Yes I am THAT cheap, but every buck counts.