I’ve been working on a off idle surge condition that is consistent and occurs approximately 1100 RPM’s. I’ve tried various fixes with no luck. Listed are the attempts: tuned A/R mixture and idle using vacuum gauge and tach. I was able to achieve good vacuum at 15-16 inch HS. Set timing at 16 degrees before TDC. Replaced accelerator pump spring. Replaced replaced HEI springs for weights to a stiffer type.