When you see timing swinging at idle, usually it is a response to some other issue, not the cause. The PCM will adjust the timing (a lot) to try to stabilize the idle at the desired idle setting(s).
Something as simple as a blocked fuel filter/injector (or anything that can cause fuel delivery problems) can cause the idle to change and therefor cause the PCM to drastically alter timing to try to correct the problem.
Running too lean at idle will cause surging.
Have you tried programming in a 100% stock tune?
Is the engine modified? Different cam? Different intake? Still using a MAF? Is the IAT sensor connected and working?
Are there any trouble codes set? Have you disabled any trouble codes?
What are the test results for "specifically monitored systems"?
What are you fuel trims at idle? Are they similar for both banks?
Regards
Paul