Intentionally I have little to no involvement in vehicle digital systems, but using simple logic in terms of some carb fuelled cars having a pump jet which under a rapid change in throttle position pumps more fuel into the inlet manifold, and which causes me to then wonder the way a similar requirement might be achieved via digital means... I`m guessing the throttle position sensor will play a part and more than likely the air flow monitoring sensor, perhaps engine temp too, even the knock sensors might be looked at and ign timing adjustment... as for what else the map might rely on I have no idea, thus it seems there might be quite a lot in play, any one of which may affect the performance..?
Given you mentioned some sort of issue relating to the lack of suck, wherever you detected that..? Perhaps with a few feet of flexible pipe of a diameter that you can fit close to your ear, the other end of which you can run round the joints and gasket locations around the inlet manifold and throttle body where extraneous air might creep in and upset the fuelling solution as decided by the map, you might just detect something... If you have a servo the pipework feeding it might also have an issue upsetting fuelling..
Just thinking in type.. in the hope it might help in any way, and hopefully not muddy the water..
