Toyota Repair: 2003 Sienna ECU reset, mileage figures, ecu reset

Question
Purchased a used 2003 Sienna a few months ago. Recently I've noticed a drop in gas mileage of 3-4 MPG. The engine runs beautifully, when at idle I have to check the tack to make sure the engine is still running. Had the throttle body cleaned, oil changed. Car has 70k. Since this car is "computer driven" would resetting the ECU possible bring the MPG back up to what it was? I understand you can reset it by disconnecting the battery for around 5 minutes. I also understand this ECU is a "learning" type of device... i.e. it may need to be reset. I also have heard that once you reset the ECU you should drive to 60 mph and then back off on the gas till it slows down to around 30, go back up to 70, repeat, then 80. This is supposed to "teach" the ECU the cars most efficient use of gas. Is there any validity in this procedure?

Thanks,
Ken

Answer
Yes the computer has the ability to relearn a driving pattern, just normal driving in both stop and go and freeway for a few minutes will be sufficient, I don't think it will change the gas mileage figures but you can try anyway. Gas mileage is more affected by tire pressures,vehicle load conditions,driving conditions and driving habits.