I was going from a stop, and I had my car at 3k in 1st gear, and I just wanted to see what would happen if I hit the gas hard, so I did and I heard this loud pop sound, couldnt tell from where, but right after that i let off the gas.

Any ideas? Is this a big problem? Or just something that will happen when I am in 1st gear.

Backfire.

Sounds normal.

Your ECU takes a small amount of time to adjust to airflow [or pressure in your case] and if you snap the throttle closed after WOT it will sometimes put a bit too much fuel for a moment.

So backfire is ok? How do I fix that ECU problem? I reset it by disconnecting the negative terminal for about an hour. OR is there another way?

Thanks!