Plug the intermediate circuit and see what that does. Don't go WOT like that, just fire it up and drive it a bit at part throttle. If that solves it then you know that you need to lean the intermediate way down. Back when I used a 3 circuit carb I had to take about 80% of the intermediate jetting out of the carb to get it to work.

You shouldn't use a 3 circuit on the street since at part throttle you'll have a lot of suction against the intermediate dump tube and it will pull extra fuel into the engine. You're best bet is to convert that carb over to a two circuit or else just lean the intermediate circuit down until it isn't killing the engine.

Do your metering blocks have jets for the intermediate circuit? If so you can easily change the jets. If you have an older carb without jets then you probably need to buy new metering blocks. Otherwise it will just be a pain to do all of the jetting work that you're going to need to do.