update :
Redid some of the welds on the board, added a ground on the E% sensor side, no luck
Since there are much more drops occurring for the 1st 2 min after a cold start, I checked my fuel pump.
Car has 30k, with 20 on ethanol, and my pre-pump filter looked like this :
So replacing it immediately jumped on top of todo list...
Did not dismounted/remounted all the connectors yet.