Macho Brace doubles your ev gain while the power anklet, brace, etc etc that you get from battle tower add 4 to teh stat (each says lowers speed but boosts attack, defense, or whatever gain) If you have a guy with the pokevirus you also double all ev gains, so on a guy with a power item they get 10 evs per kill from a guy who normal gives one. There might be a section in here describing it a little better than I can but if you need a virused guy so you can spread it just let one of us know and we'll trade you one