Did the car completely cut out, or did it just plateau?
]Way back when I was in high school, my mom had a 90 Buick Century with the 3.3L (I've heard it's essentially a 3800 with a shorter stroke). I took it out for a drive one day and had it hitting the top speed cutout (speedo only went to 85 in that car, but I think 109MPH is a common limit).
Anyway, I hit the limit a few times and then boom, ratttle rattle. The car sounded like a damn combine. Turns out one of the pistions shattered!! Good thing the car only had 28K miles....free motor!!