No pwer an stops when warm

We purchased an Agila which used to loose throttle when driving. Took ages to find out what was wrong as no codes were present.
I had to look closely at the live data to see the lambda sensor was giving wrong readings.
After three aftermarket lambdas still no joy, then I bought a top quality sensor and it cured the throttle response and dying.
Not saying this is what yours is doing but its the same breed of car with the same engine.

Have you had the codes read? Some can be present without putting the light on. Also sensors can be giving a false reading so the ECU won't throw a light on