advanced timing, anybody else doing it? Options

[6strngs]

so, after having read about how advancing the timing a couple of degrees on this car can make a difference, I decided to advance mine. took only a couple minutes and my timing was set at 15 degrees BTDC. my idle now sits at about 900-950 as opposed to about 750 like it's supposed to be. but when I started driving I felt the difference right away! it's not uber dramatic but it's noticable. especially in the low rpms, from like 1-4K, and it feels like the normal power drop at 5500 isn't as sharp, I mean, it's still there it just doesn't feel like it drops as sharply. I'm running 91 octane gas with and I didn't feel/hear any detonation, even when I tried to put the car under load by riding it 4th at 1400 RPMs I didn't notice any. I'm thinking of either going back out and setting it to 16-17 or just using 89 octane. anybody else done this?

[alltracman78]

How many RPMs per * timing I have no clue.

Here's the thing though.
The ECU [ECM] does control idle speed via ISC valve and ignition timing.
However, with the valve fully closed and the timing as retarded as it can get it, the ECU can do no more.
Once you change the base timing, the ECU can only adjust so much for this.
Every engine will be a little different, but the ECU only has so much leeway it can work with.