Nightrider XIED's were the first change I made to my 2007 FLHX. They've worked just as advertised. Bike ran noticeably cooler without much of a hit on mileage. For a relatively stock bike they're a good deal.

 

I went with XIEDs on my new 08 UC. At 1000 miles, and since I had some money left over, I changed the AC and put on dresser duals, got a SERT and had the bike dynoed. Was expecting a noticeable improvement but, I was disappointed. Plan on doing a little more to the motor in the future, so not a total waste of money on the SERT. But often wish I had just saved the money and stayed with the XIEDs