Idle oscillation / firing angle complication

Ok so I’ll start with a bit of info here .

im running a haltec elite 2500 on a SR20det ... the base map from haltec had the firing angle pre set at 109 degrees .. the car cold started and idled flawlessly at 850 rpm +/- 50rpm.. the idel was as steady as anyone could dream of ... when I got on the dyno I went to lock timing at the preset degree of 20btdc .. at idel I had a decently stable mechanical timing (Timing light ) around 20btdc after adjusting the CAS... all seems good ... but when I rev the engine up a bit to get a very stable reading the timing wanders 10 degrees away even tho I have it set to locked timing... so what I ended up doing was adjusting the firing angle to 99 degrees and this had me right on the mark ... I have timing locked at 20 and I see 20 on the light at any RPM so I’m assuming the firing angle was wrong ...after double checking when the timing was unlocked that I was seeing the same reading on the crank as I was in the base timing table I figured I had it where it needed to be to get accurate timing adjustments .... this is where the idle began to oscillate from 800rpm to 1300rpm and up and down and up and down ... what I ended up doing was turning off closed loop idel control and the idel began to stabilize at around 1100rpm witch is a bit higher than I’d like ... i have played around with the PID and no matter what I do I can’t seem to get a stable idle anymore not even in open loop ... is it possible that the firing angle may be correct at 109 ? And if so why would the timing wander away from any set point when in the LOCKED mode ? I’m feeling like something isn’t right due to the fact that everything used to work flawlessly before I changed the firing angle ... I just wanted to make sure that I was getting the timing I entered in the base timing table and not getting 30 degrees when I want 20 ... the car made great power at 500HP to the hubs on a mainline hub dyno ... hopefully you can shine some light on this for me ... I know you guys have an SR if your own in that 350z

Using the wrong edge for a crank signal will cause the timing to change slightly with RPM. Another one is ignition delay (the small delay from when the ECU triggers the coil, and the spark actually occurs -- perhaps your ECU has a setting for this).

Thanks for the reply David , I’m running an elite 2500 so it has a lot of capability’s ..after a bit more tinkering with it I’ve gotten the idle to stabilize again around 1100rpm after turning off O2 control ... soon as I turn it back on the idle starts to oscillate again .. so I’m assuming the settings in the O2 control need some adjustments .. it is only stable in open loop idle control so I’m thinking the PID may need some adjusting ... haltec is guna remote into my computer and help me sort out the issues and when I get to the bottom of it I’ll post the cause and fix for anyone in the future to read