Auto X techniques

[mojoyaris]

I was at a Test n Tune recently over the weekend. It had a few of the basic elements, Slalom was one of them. This slalom was about 38 paces in between cones so it was a long slalom with about 5 cones.

By the time I got to the 4th cone my brake pedal went hard and wouldn't press down. (Left foot braking technique).

Has anyone had this problem with the throttle on and using the left foot braking technique to balance the car around the cones?

When I took my foot off the brake the pedal went back to normal. The brake would only go hard if I had the throttle on and after a few cones into the slalom.

My other cars wouldn't do this, just the Yaris.

I was wondering if it was something that is built into the car or if it was something to do with my master cylinder or brake lines.