IMO there is no reason to run the thicker oring if the original is in good working order. Take a picture of the Jack's oring on the pump without the spacer and then put it in the pump housing and take a picture so we can see how far the oring goes into the pump housing. You just want to avoid the ability of the oring to pop out of the pump basket due to the pressure, which is why the spacer is used.
I actually ended up putting the regular o rings that day when i got confused about jack's.
This was two weeks ago and couple days ago i got that nasty limp status 2 ( STFT hitting 120%).. Orings are lubed and everything was installed correctly..my doubts are these DW300C need to be hardwired or something cuz it happenes only after some pulls then when it gets cool down it goes back to normal..
Now it's either i have some leak in the Orings area, or i got some defected pumps or they truely need to be hardwired.
Filters are clean and not clogged.
1050cc bosch injectors seem to be fine (both banks are balanced)