It seems to me that it is a problem or with the tuning, or with the regulation of valves, but that theme that is happening to you is a bit complicated since the failure is a bit difficult to find, it happened in a fiat Fiorino and it was for the regulation of valves, and in another similar case with black smoke and everything, but in Renault Twingo it was the set or draft of distribution, when it is much As difficult for the sensors but it is always good to run a scanner to rule out, because I also spend a fiat point and the problem was the central injector that did not sealed, that is, it did not have pond, you have a simple test first to rule out a couple of things, take out the filter cover and open the contact should not pass fuel to the throat until it starts if the seal does the seal of the injector, it could be easy. Good luck and eat us. If after you try everything nothing works put a mechanical carburetor from Peugeot hahaha to anything friend.