The ECC cars do have a ECU, under the front passenger seat (at least on UK cars). You also have a lambda sensor on the exhaust, the carb is significantly more complex, the distributor is different, and so on. It is a full engine management system, without injectors.
I personally am of the opinion that the Weber makes no difference to a standard MA10 or MA12. Well, no positive difference. I'd say it definately makes cold weather starting harder, and has a habit of not working quite right.