Looking at some of the web sites that discuss ECU tuning, at least one says that by upgrading the ECU the engine not only develops more HP and Torque but is more efficient. Is this so? While I expect there will be members who will say, if you wanted great mileage get a Civic, I have always liked the fact that Volvo builds cars with good or very good performance with good mileage. Most of the time that I drive my R I am commuting and I am not using anywhere near the car's maximum performance. If I upgrade the ECU, how will this effect fuel efficiency in normal operation? Is there a perceptible difference.