I will put this out there, as it was my experience with NGK plugs a while back......I have used them from daily driver to bracket racing and even N2O racing......My experience was when they saw too much fuel, they just plain quit. Like the added resistance to light the fuel some how made the box put out a little more juice to light them, and it burned out somthing in the plug...Mine would not come back. And like you, it was generally the same plug positions over and over. I really hated those things when I figured it out. I have tried a lot of plugs since then.....

My favorite now is the Autolite Racing Plugs AR3935 (I think thats the number) I love those things. Season after season, no issues. Fire the car in the dead of winter, fuel puddling all over the place...still lights....Now those are like an NGK7 I think, but they make an AR3934 which is an NGK8 equivalent if I remember right.

I used to buy three sets a year.....Now, I buy one set, and it lasts me two years.

I would [censored] can the plugs and try a set of these.