Yea. I called KW and talked to them a couple months ago and the guy mentioned they made the ST c/o in the same factory and everything the same as the KW v1 except the metal used was different, hence the KW lifetime and ST 5 yr warranty. I think its worth trying for $800. I dont ever plan on tracking the 6, ever. For any reason. If I wanted to track I would get a car I could track or borrow a 370z. The 6 is dd.I was actually torn between the ST & ISC coils as i could have got either for ~$800 CDN all in. Rather glad i found the Mazdaspeed ones though.
I had read on other car forums about Swift spring upgrades on lower priced coils, and guys seemed to like them.
The only reason I heard about fortune autos was because my best friend has a 370z nismo and he told me those coils with swift springs were popular among z owners and he told me they made them for the 6.