Verification of Vacuum Probe

I had to be sure of what I was seeing.

This was taken from a 95 Nissan Pickup 2.4 PFI 4cyl triggered off number one.

Removing number four spark plug proves it, the number four peak is missing.

In this image from a 92 Honda PFI 4cyl, (red ignition spikes, blue injector, gray vacuum pulses) number four injector fires at number four vacuum pulse, triggered off number one ignition.