Symptoms sound very similar to ones I've just had on my 8valve, mine idled smoothly but you had to slip the clutch to move off in order to avoid Kangarooing, then was ok with plenty of right foot. Took it to Peak Alfa, and he found the big diameter hose after the airflow metre was split around one of the flexi parts, just run the engine and put some pressure on the hose caused the engine to almost stall. When setting off the engine moving on its mounts was causing the split to open up and let unmetered air into the system. Part cost around £30.
1994 White 155 2ltr 8v
1972 GT Junior