I've just discovered a new way to gain extra speed on the track, especially in Winter 4 of the main Winter Campaign. I noticed that rapidly pressing the steering buttons gives the car a significant boost in momentum and makes it go faster. I got this when I was racing against Youngfella on Winter 4 because he's very fast and I couldn't keep up with him.
Here's the new trick: Go to settings and you can add two separate buttons for each direction, left and right. Then, you can press these buttons alternately, and this actually increases the car's speed, especially in Winter 4!
I used this trick in my latest run to set a new record!