Knock sensor and related connections could be an issue as well! (rough idle, low power, bad economy)
Please see my earlier post how to pinpoint the problem.
Only in very rare cases the ECU and even a sensor fails (but they do fail), it is far more likely a connection problem. In my case I had all kind of connection problems, you can easily test it with a meter. You might get away with a cheaper meter, but something like the general fluke 87 or the more expensive automotive 88 could be it; depending on how much you want to get into it and what works better for you. I bought 3 cheapies before, so I wasn't that smart to begin with. But if you are (unlikely to me) not keen of electrons, it might be better to get somebody look after the car.