WOW! What a difference. The car now starts much smoother and no spark knocking anymore! I couldn't believe how fried the original NGK's were after 55,000 miles. I picked up Bosch Platinums since the parts store was out of NGK's. I can't understand the price difference. $2 Each for Bosch and $13 each for NGK And before you ask yes they are platinum plugs. The job was well worth the money. I got the coils online from a place callednissan-parts-auto-dealer.com for $48.47 each which I thought was pretty reasonable. Anyway just thought some of you who have this same problem might be interested. The fix is really pretty easy. If you can work with basic hand tools you definitely do it!