Does the 2.5mm x 5.5mm plug go in the positive or negative position?

2000 Pontiac Firehawk. I have the SLP version of Diablosport.

I modified my axle ratio from 3.42 to 4.10 and it seemed to update fine.
Now I can only go 20 feet and my motor shuts off. Do I also need to modify the tire settings when I modify the axle?