M3 almost fell off the road yesterday~help

Tried to open it up for the first time (DSC off, sport button on) and do a second gear pull last night in my new coupe. As soon as i hit the highway straight it pulled smooth up to about 6500 rotations, when the rear end lost all control and swung left to right. The car is not stock but it does sit on 20"x11" rear wheels that theoretically would help hold it to the road. Im coming from an STi so im certainly used to all wheel traction, was this simply a lack of traction in the cold North jersey weather or something else i should be concerned about ?



Thanks everyone.