Whirlwind 200RV Idle

What has been the experience of those running a Whirlwind 200RV related to engine idle? On my O-360-A1A the lowest smooth idle I can get is 650 -700. Anything below that and the engine runs rough and will tend to cut out. It runs very smoothly at 700, a little less so between 650 and 700. The engine has a newly installed Avstar 10-3878 carb. Thanks

idle cutoff

Should not be able to kill engine with throttle.

Also, if impulse coupled mag(s), about 650 is range where timing changes.

Link -

The engine has Slicks...so it sounds like what I am experiencing is normal, correct? Thanks