Idle surge

I'm having an issue of having idle surge when trying to achieve reasonable AFR at idle. Whenever I have the car anything richer than 13.3 the car idles like a champ but when I try to lean it out it the rpms dip as low as 600 then surge to 1300 or so and this repeats until I richen the mixture.

Car is a Dodge Neon srt4 2.4 L with a fuel tech ft600 running spark pro 2 with factory coil pack, Siemens Deka 888 cc injectors at 43.5 psi fuel pressure on VP c16 fuel. Fuel pressure is rock solid.

The issue occurs with or without idle control active.

I've tried timing anywhere from 10-20 degrees and I've triple checked injector battery offset values.

This is with the car full temp with no additional fuel modifiers that I can identify affecting fuel. I know ECT and IAT aren't for sure and it's well after post start enrichment times.

If needed I can add a datalog of this condition.

Yesterday fought a very similar problem with a LSX swapped BRZ. Adding air (DBW settings, but your IAC should allow a similar solution) and reducing timing was the solution for me. Now I was still running with a richer mixture, and haven't tried leaning it out, nothing I tried was working until, I let the idle control timing work to control the RPM and opened up the air.

At idle, the timing can be running -10 to 10 deg.

Hope that helps

I have no issue having the car idle with or without idle control with richer AFR it's when I try and lean them out.

What injector pulse width are you seeing at idle? What injector information do you have?

Also, what injection angle are you using?