[fordguy40]

Thanks everyone for the suggestions....you guys were pretty much right on. All the screws holding the carb together could have been tighter, but there were a few other issues.

The filter looks okay and everything, except the chassis-mounted hard lines and tanks, is new so I'm tentatively ruling out a fuel system issue. Retorqued the intake, and it's got hydroboost. Vacuum gauge was pretty steady at 19 when I was setting the idle mixture a while ago, but I didn't check it before I pulled the carb off.

The high idle screw was definitely holding the throttle blades open. Probably the result of my advancing the timing and not readjusting the fast idle.

Float level was also set too high. Misread the instructions that came with the rebuild kit and set it to 3/16" when it should be 3/8". Funny thing is that the float level was similar to the float I pulled from the carb when I rebuilt it, so the last guy also biffed the setting.

Swapped the throttle shaft from a carb I picked up from ebay so I could reinstall the throttle lever actuator to complete the emissions system, and it turns out to be a tighter fit than the one it replaced, so I'm hoping this reduces the unmetered air coming in. Waiting for new air horn and throttle body gaskets to put everything back together, but will update the thread once it's back together.