breather should make no difference unless it is touching the accelerator pump or pinching the fuel line??
anyway tuning brocedure is always done vacuum line off and pluged at the carb. set total to 36 deg and drive setting up carb and seeing if it pings then maybe go up to 38?? later you can try and add vacuum in. if you are using vacuum to hold up idle it will drop off and run like crap. also at WOT there is no vacuum so it drops away and no power.