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?

[Bitter]

yes, but what i meant, and sorry i wasnt more specific, is that 5 degrees shouldnt raise his idle by 200 rpm. the idle is set by the PCM via the IAC motor and several sensor inputs. at 20 degrees base timing my idle was the same as it was at 10 degrees base, and at 15 degrees base its still the same. the PCM will adjust. its not like the idle speed is set by a screw holding the throttle plate cracked, or some other mechanical device on these engines.