I would get it T4'd before swapping the ECU out, the ECU on the 1.8 nasp is not to my knowledge as susceptible to failure as on other models in the range. Has the car previously ran ok in your ownership? My Rover 25 1.4 came to me with a similar problem, the main culprits were found to be a maladjusted throttle cable and a thermostat which had been rendered useless by holes that had been drilled through its frame. I suspect under previous ownership that the inlet manifold was swapped out as a job lot complete with everything that is fitted to it so the IACV is not set up correctly for my car. As a result I still get the occasional stall when driving off from cold in the winter but otherwise it runs without problem. I hope to get it fully sorted eventually, it will need T4 or a diagnostic tool that can do the job of setting the IACV with the ECU but I do very few miles and for my needs the problem remains on my to do list on an opportunity basis.
