Are you sure those plugs aren't "Commercial 44" plugs. AC delco had Commercial plugs that had a larger electrode, and no resistor. The commercial plugs were used in vehicles that did not have a radio. The resistor plugs were used to supress radio interferience in vehicles that did have radios.
Today The commercial plugs are of very limited availability. Even if your vehicle doesn't have a radio, you likely do in your cell phone. Of course you should never be on the phone while driving without some sort of handsfree device.
If you can get the commercial plugs, get them! Why? You could always teach the prius driving i phone user a lesson when you drive next to them!
