There is no easy or cheap way of getting consistent high octane with boosters. The best way is to buy high octane race fuel at select stations.
https://www.sunocoracefuels.com/fuel-finder or to pump it yourself
http://www.racefuel.com/vp-ms109-rac...el-101-octane/
I don't know where you live, but Sunoco sells 100 octane at select stations (under lock and key). When you get there, just make sure you pull your pants down, and grab your ankles...
IMO, high octane on a stock street driven M6 is overkill. And I can ensure you will not feel the difference. Open your wallet (expect $150 for a full tank) and see for yourself.