I changed the carburator of mine A14 and put it a A15 carb, the problem( or not!!) is that it doesn`t have that diaphragm of the throttle opener. Do i really need that because of the others emission control devices? there`s some disconected hoses but doesn`t seam to affect the engine work.

Got a picture? Your question is not entirely clear in english.
Probably the words are technically correct, but not the right words for the carburetor parts.

I can`t take pictures yet. But the thing`s missing in the A15 carb is this:


(the arrow in the bottom Throttle Opener Vacuum Motor)

The Throttle Opener is not needed for any engine. It is for emission control, and no other parts depend on it.

Yes the engine runs but is not as smooth as before.

Two weeks ago I fitted a 1980 A14 carburetor to my 1972 A12, and it runs smooth again.

I don't think it would be the fault of the exchange carb on your engine, as per say if it would match up or not. Probably your dealing with a 30 year old carb that would have to be rebuilt with a certain level of expertise and have it sleaved to have it run properly. If you find one that is in good shape and cared for properly, you may get a decent running engine - but it won't run as it had been intended to 30 years ago. If you desire a perfectly smooth and reliable engine you would need a new carb on top of an engine with strong but even comression and a good distributor.