Mobile Swimming Pool

[Wolverine69]

Hi everyone can anyone help with this prob.
Have recently been having water running down the cables in the passenger footwell this has been blowing my ECU i am currently re locating the ECU to keep it safe but cant for the life of me figure out where this water is coming from it only does it when i get caught out in downpours, someone suggested it could be the heater matrix and if so is this a big job to fix or does someone know of a specialsit that could sort me this problem out as i dont want the car to rot it is a 94 RX7 import.