Bad connections or cables. Clean connections till they are shiny and inspect the cables for damage. Replace if necessary. Less resistance with the plugs out (no compression to fight) will let the motor spin faster. With the plugs in you are fighting the compression as well (more resistance)
I'll start with the connections and cables,the battery is new,I just took it off my G3 with a 48 spl and it was fine with that one,thanks for the replies.