Cheap champion coppers, old technology for old technology. Tried the fancy Bosch and NGK stuff and fine wire iridium with disappointing results. You know you made a big mistake when sixty four bucks worth of fancy spark plugs runs worse than the eight bucks worth of dirty old champions you just replaced...

 

Like most have said, cheap champion coppers are ****. Haven't changed mine I a few years now and it still runs great. Probably about time for some new ones though.

 

NGK BPR6ES I have them in both my 97's I had lots around because they worked in most of the rear drive Volvo's , never had one mess up which I cannot say for bosch ,