That makes sense, when I first got my eclipse (sorry for the lack of a better example, but its the last car I actually had a chance to do some tuning to and im new to the supra) I reset the ecu and it actually became faster, but once I started to modify the motor and the ecu had made adjustments to accommodate for those mods, resetting the ecu actually slowed the car. The difference was very minimal at best though and at the track an inconsistent driver wouldnt have been able to measure the difference. In the long run though, its best to leave the ECU alone and let it do its thing, it is already made allowances for the mods that you have done for the car to get the best it can produce out of the mods available. The ones that have modded the car and then reset the ECU and the car felt faster is probably because the ignition maps were reset to stock (advanced) and the car made more horsepower, but it was not as safe as when the ecu's programming was untouched