I never had the cruise control malfunction again, but I could repeat the brake issue. Yes, these are two separate issues. But the brake issue prevents the driver from being able to stop the car.
When the car took off (I was on an almost-empty Interstate highway in Texas), I tried to brake and couldn't move the pedal. I put both feet on it and pushed as hard as I could. In the gym, I could push 600 lbs on the leg press. I could feel the pedal arm flexing under the pressure, but it would not move downward. I regained control of the throttle when I shut off the cruise control - leading me to believe the cruise control is at fault.
I demonstrated the brake problem to the dealer. They replaced the master cylinder assembly. As I drove away, someone pulled out in front of me and I could not stop for several seconds. Once again, the turbo was generating positive manifold pressure and the brakes would not move. After the manifold pressure went negative, I regained brakes. I took it back to the dealer. An older mechanic took a look and he said the check valve was worn. Once replaced, the problem vanished.
Event 1 - runaway acceleration and zero brake
Event 2 - zero brake on boost
Event 3 - zero brake on boost.
BTW - I have raced motorcycles and cars for years, so I was quite comfortable with the car going fast. Being alone on a sunny day with no curves in sight gave me plenty of time to ponder the cause. I knew I could turn the engine off, so I wasn't in much danger. I was able to evaluate all the suspected causes. Feet on the wrong pedal? Nope. Floor mat or stuck linkage? Nope - it was easy to move and quite loose. The only other thing connected to the throttle butterfly was the cruise control. That's when I tapped the brakes - and discovered it wouldn't move. That's when I realized I was dealing with two faults. Glad I had a dashboard switch to shut down the CC. I was pressing the brakes, and suddenly it started to give slightly. I noticed turbo boost had just gone negative. I hit the gas, built up pressure, and sure enough the brakes wouldn't budge. So that part was very repeatable.