I have always liked the SteelFiber product. I have it in my #3 and #4 irons. Multiple weight options available. If you want a similar weight to the Tour 90 KBS, the Steelfiber 95 or if you want just a little lighter, the SteelFiber 85 could work. I also like the Recoil Dart and there is a 90 gram option. Finally, and at a little better price point is the Rapport core Blue Iron shafts. we developed these with VA Composites and it has really performed well for us. the R flex is a little lighter at 75 grams, but if you were looking at going a little lighter, it might be worth a try.
Britt Lindsey