9n 1.2 Engine light after motorway run

[merseyside bossman]

My 9n 1.2cc, can run around town for weeks on end with no probs.
Once upto speed on a bit of a motorway run the engine light will come on and it will run like a dog
This has happened twice?

Any ideas....
Ive replaced the water temp switch and air filter.

[akz786]

First point of call would be to get VAG-COM onto it as this will highlight any fault codes...
- Check the coilpacks
- Also check the lambda sensor and flexi pipe are ok.

Hope this helps