Also, there's an o-ring on your mix screw. If it's old (original) and all hardened up, the screws may not function properly. The o-ring seals the screw into the carb body and if it's bad, you may be sucking some air in. That might explain it running better with the mix screws 4 turns open.
Last thing is the butterfly shaft seals. They work on vacuum, being sucked in tight and sealing by the air flow through the main bore. New, they are very soft but they harden up with age and don't work so well anymore. The faster you go (higher RPMs), the harder they get sucked in and the better they seal. That means at idle, if they're old and hard, they may not work very well.
If your carbs are U.S. spec with the fixed needle, you could also probably do with another size up on the mains. If they are Canadian spec carbs with the adjustable needles then the 135 may be fine. Also, if they are Canadian spec carbs, you may already have smaller air jets. The U.S. carbs got 135s but the Canadian ones may have 130s. If that is the case then I'd look at the rubber bits, they may be your issue.