I have a standard F5 that runs a little flat at mid range and top end and am looking at clutching options. Dan at the outdoor shop sells a kit which improves mid and top for $149. I don't know whats all in it, Im waiting for him to come back from the show. Jeff at Dakota Perf. sells one for $86.00 and he grinds your weights and includes a helix. He suggests stock springs and two jets leaner. Jeff says 350 rpms higher engagement and pulls hard. My question is; Have any of you tried these kits and which do you prefer? Thanks for your help.