To get the super racing muffler beat the Hot Hatch Event in the 2nd season.
If you already ran this race in the 1st season, you can't unlock this part.
3rd NA Tune - Win the Group B race in the 2nd season. If you already did this race in the 1st season, you can't unlock this part.
3rd Turbine - Win the Touring Car Event in the 2nd season. Again, if you already ran this race in the 1st season, you can't unlock this part.