I have an '86 Bonneville with the 305 V8 and it'* got about 196,000 miles on it. Just lately the choke light comes on intermittently. When it does this, the oil pressure and ammeter gauge needles move to the left and then move back to normal position as the choke light goes out. I have no idea what this means? Any ideas?

On my ’84 camaro, the carb has an electric choke heater that helps to fully open the choke when the car is warm. A choke heater relay is used to apply power to the heater.
The coil for the relay is powered by the voltage signal wire to the alternator. As a result, the “choke” light came on whenever I had low battery voltage or a problem with the alternator.

Not sure if your car has this arrangement or not. (I used to have an ’86 Pontiac Parisiene and I think it was the same but not 100% sure because I never messed with it).

If it does, I would check the following in order until you find the problem:
1. Charging system (battery, alternator, cables and connections)
2. Open circuit on choke heater element
3. Choke heater relay coil resistance (mine went bad once having low resistance).
4. Wiring connections under dash – including grounds.
________
Also, you said your car has an ammeter? I thought these cars only came with voltmeter. Do you have an aftermarket ammeter?

It'* probably your alternator, or more specificly, the charge indicator wiring on the alternator (pin 1 on the 2-pin connector on the alternator case)

The choke relay is being fed not to ground, but to the charging pin on the alternator. It sounds like a goofy arangement, but that'* the way GM did it to run the choke heater on Rochester carbs....in other words, when the alternator is working, the choke is automatically turned off. It uses the changes in resistance to act as a cutoff switch to the choke. (Unlike a Holley or anybody elses electric choke that is run off a hot in run circuit without any relay involved.)

The trick to figuring this out is ignoring the choke lamp, and focusing on the sudden dip in the electric oil pressure gauge and voltmeter...both indicating a voltage drop in the electrical system that coincides with the choke light comming on.