There’s a sewer tunnel under this Checkpoint that may house several freakers. This checkpoint is practically safe as long as you don’t make extensive Noise.
There’s a total of six speakers here, one on each of the guard booths facing the tunnel and the road, and two on each of the two MMUs.
The gas can is right in the open, behind a parked school bus while the generator is found inside the fenced area near the tunnel as shown below. The NERO Injector is located in the MMU near the generator.