I run 07 Buell plugs in my Sportster to get around a pinging issue under hard acceleration,they are a cooler plug,really helped,they are a 10r something,Harley plug,the sport uses the same plug as my 05 EG,but no pinging issue with the 05,or I would put those plugs in there also.
At 8k miles I installed NGK plugs in my ultra. Soon after the check engine light started coming on. I took it to the dealer and the code was that the rear cylinder had miss fired. This is a common thing I was told. I did some research and changed back to HD plugs. This ended the problem.
Maybe I did not have the plug wires pushed on all the way. I took the bike to the dealer three times to have the codes cleared. They could not find a problem. The bike ran fine, I never noticed a miss fire.
Try a different brand and if you have the same problem you can always go back to HD plugs.
Keep in mind that the plugs and wires are a part of the Ion Sensing system that HD uses as a means of detonation sensing. Plugs that offer a resistance that differs from stock could cause performance problems.
I was thinking about the SE triple platinum. I have always run a platinum plug in my other vehicles. Just a thought. I am getting ready for my 1000k (actually 1500) change to a synthetic oil, do my stage 1, pipes and was going to do plugs too.