Slp stage 4 VS bikeman Stage 3

I'm not a big fan of either but IMHO stay away from bikeman
SLP is ok.

SLP vs Bikeman

I can't tell you about the Bikeman Stage 3 kit, but the Stage 2 kit that uses the stock cylinder, a ceramic pipe designed specifically for high altitude, high compression heads, PCV and a Team Tied is a very good package. It provides huge gains in botom end and midrange torque and far better than stock power on top. We ran the sled bone stock on big hills against several Etecs before and after installing the kit to verify the gains and it flat works. I will be running their 860 kit next year.