I got one of the 5 wire kit here. While the customer service was great, but the fitment was so-so (wrong size washer) and the actual gain from them is margainal at best (if anything). I installed the kit at the dyno, didnt gain anything. On one of the run, I actually lost 3hp, but in average it was within 1hp and 1ft-lb of each other with or without the ground kit. I guess this is one of the item that is not bad to have, but its not necessary to have it at all. I would love to look at one of those HKS kit and see if they are any better
It didnt smooth out my idle, my idle still jumps up and down