Kattumaram

Those vehicles that employ EDIS-6 or EDIS-8 ignition systems (such as my '97 XLT) where two sparkplugs are fired simultaneously normally require special plugs on the right bank that have platinum-loaded ground electrodes.
Those plugs are fired in the reverse to normal polarity, the center electrode is (+) and the ground electrode is (-), and the ground electrodes tend to erode rapidly unless they are platinum-loaded.

I have installed Bosch P+2 plugs in my '94 Lincoln Town Car 4.6L EDIS-8. The plugs now have 30K miles of service. They also DO NOT have platinum-loaded ground electrodes, so they would not normally be recommended for service in EDIS-6 or EDIS-8 systems.

Today I pulled #1 plug to check the status of the ground electrodes and I was surprised to find no significant erosion. It appears that the plugs will provide at least another 30K miles of service before replacement.

Conclusion: In my experience Bosch P+2 plugs do improve fuel mileage and give a smoother running engine and will give at least 50K miles of service in EDIS-6 or EDIS-8 systems.