I have the same proble with my Jeep Grand Cherokee, it stalls when I am driving the car and at stop signs. I took your advice and removed the resovoir, found the box with the grey, white and black connectors, but I am not sure which screws need to be loosened and changed to the 1/4".
The black box with the three color conectors has two screws on the left and one on the right of the box. I loosened all three of them but they are very long screws. There are two other screws that are located further to the right, one on top of the other, with the nut showing and the bolt located behind the metal.
Am I in the right area?