Off idle RPM surge Crusader 5.7 HT

[wlw209]

I have a 5.7 HT with a Holley carb. I have adjusted the idle and have good vacuum. She idles well until warm When I go above an idle (1000 to 2200 rpm) the motor surges about 200 rpm. She run fine at crusing rpm but idles low when you come back after a sustained run I have 20" of vacuum at a 880 rpm idle. Is this the power valve or ??

 

[makomark]

check the ignition advance mechanism - worn weight, broken spring.