it is located on the lower left side of the timing cover
The fuel pressure regulator in that 96 GMC 4.3 TBI is located in the throttle body.
I don't know about the Jimmy, specifically, but the fuel sensor on most fuel injected cars are located inside the gas tank, as part of the fuel sender (pump).
You have a problem with the EGR system, the pintle positon circuit.
i think 35mm
It is screwed to the engine block. Crawl under the vehicle and look for it which I suspect you have not done. If you cannot find it then you are not looking hard enough.
Hand brake? I thought the last GMC with a hand brake was in 68, but I could be wrong.
When owning a car, it is important to know and remember the gas tank size. The 1996 GMC Jimmy has a gas tank that holds up to 19 gallons of gas.
a defective starter switch
Probably a crossed wire or electrical short.
It is on the left side of the dashboard,you can only see it when the door is open
The brake lights on a 96 Jimmy are operated by the brake light switch, mounted on the brake pedal assembly. If the switch is bad the lights could stay on or off, or be sporadic.