I never noticed it on mine.
------danevoIV said:no m8 it wouldn't be that, the fan only comes on when the car reaches a certain temperature not when you accelerate hard, the extra load will most probably be your fuel pump as it has to flow allot more litres per hour when your floor it, however no matter what size your battery, your alternator should be able to produce enough power to run everything and still charge ,I wouldn't expect the lights to go dim, so you could have a problem with your alternator if why don't you get a volt meter and see if the battery is charging properly for starters.
Yes, I did that.Spanpody said:Just a quick suggestion.
You did reconnect the ground connections (held in with one of the ECU bolts) when you bolted the ECU back inplace ?