Damn you F&F!
It's all good. The flames occur when your air/fuel mixture is too rich (extremely rich). If you ever watch road races/autocross on SpeedVision, you'll probably notice flames coming out the pipes of some cars when they downshift around a corner or something. Or... Tokyo Extreme Racer Zero... that game has cars that spit flames when they downshift. But yes... it's caused by a rich air/fuel mixture.