Just posting to eliminate any fears, and to clarify things for any noobs like myself..
When I reset my ecu for the first time it was a huge success.
I have R33 gtst s2. with standard ecu, aftermarket alarm, turbo timer, FMIC, exhaust, stereo, and thats just about it..
I disarmed/unlocked the car. (did not disconnect any alarm wires or anything)
Then disconnected the negative terminal from the battery.
pumped and held brake on for a minute. turned light switch on/off a bit, to use up residual power. Then left sit for half hour.
Reconnected battery, checked clock to see if reset, it was now wrong time. 1 o'clock which i thought was weird... My stereo had not lost its pre-programed radio stations, but it had switched from USB input to radio.. also weird....
Then tightened terminal connection after turning everything off. While tightening up terminal the timer turned itself on along with the radio. last weird thing....
I then started the car and noticed the standing idle had increased from 800ish to 1100ish, as i had been told it would if reset was successful.
Then took it for a low paced casual drive through town (basically the softest it's ever going to be driven, like my gf drives it) out to an unused straight road..
I then exercised the throttle through the rev range. Held at about 3k a few seconds then off, slowly up to 6k then down, etc. (not really sure the best method, but have read to to this) Then basically ran a drag race up to 5th gear twice. Then had a bit of a spirited drive up and down the gears.
Then cruised back to town sitting on about 100kph. followed by another slow drive through town to fill up tank then home.
The drive seemed to have more low rev power and be more responsive. The next test is to see if it has improved overall fuel economy.