1991 Chevrolet K1500, 4.3 V6. Plugs only have a few hundred miles on them but are Fowler. Two reasons, it’s t it burns oil due to bad valve guides. Second, vehicle was running rich due to a missing emissions component. I installed an oxygen sensor spacer this evening. Vehicle runs quieter, more power, and shifts smoother. If it was running rich due to the need for the O2 spacer, will the plugs eventually clean themselves up? I plan on running a heavy dose of Seafoam as well.