Recently did a engine swap on a 98 k2500 with the vortec 350 with automatic. Truck came in with a locked up motor so we don't know if this problem existed before hand but owner doesn't recall anything like this. Year of the donor truck was also 98. Truck starts and runs but as soon as you press the brake pedal more than half way down it will shut off. If you lightly press the brake pedal you can stop the truck with the brakes and it will stay running. If you press the pedal more than half way to where it starts to shut off you can let off the brake pedal and it will stay running. It will idle and run all day long fine with good oil pressure. We pulled all the abs and brake fuses\relays and the problem still persists. No codes no check engine light. It seems like the brake switch is either cutting power to fuel pump or injectors. We also swapped throttle bodies from one to the other with no difference. Anyone ever had this problem?