First of all: You shoud get better performance and better milage with this carb. This is a prooven fact, lot`s of guys did it and you wil do it to.
Now that you got som peace of mind
let`s see:
1. check your linkage.
2. make sure all the different holes and tubes for vacuum asessories are closed. You got one for the vacuum advance (that you hopefully use) plus there are 3 others that you don`t need on a 235. Close them with a rubber cap.
It sounds like air is leaking in to your carb what messes up the metering and everything.
For a quick test idle the car and spray some start spray or break cleaner around the carb (make sure it gets not in the airfilter) if the rpm goes up you got a vacuum leak.
If this shows no results check your choke.
What kind of choke you got?
Frank