I'd suggest slowing down.
Also wouldn't just start throwing coil packs or anything expensive on the car.
You should give it a solid tune up. That's a given. I'm not convinced that's your problem though if it's only doing it at high speed and no other ranges. It would be a good idea to get a good scan tool (if problems still exist after tune up) and monitoring what's doing what at the point of failure and at normal operation.