The rust color on the insulator is normal for a very old plug. They do that usually after they've been take past their normal interval. Have a look in the supressor to check if there's any corrosion in there.

The plug tip is very worn, they've gone too far past their normal interval (i think it's 60,000km/40,000mi from memory). The ceramic looks about the color i'd expect for the 119 v8, you don't want it too white (too lean)

Which ignition system do you have? twin coil? direct ignition/8 coil packs? If you have twin distributors then check the distributor car and rotor for wear and replace if required.

Check your suppessors for correct resistance (with direct igniton) or check the whole igniton lead (inc coil leads) for resistance (with twin distributors).

This is a good step forward to finding your rough idle. (mechanical or efi fuel system btw?)

__________________
Alex.

MB Tech
Sydney, Australia
Volvo 122S
W201 190D 2.5 manual
W202 C240
W203 C32