idle surge

[SEA320]

I posted this issue awhile back, but still having an issue. wanted to provide an update to see if there are any new insights.

I replaced the O2 sensor and the fuel pressure regulator to no avail. engine harness is new. tried cleaning the air mass meter, didn't help. The onboard computer spit out several codes; 4, 6, 9 and 16, cleared those, then got a code 5 (egr). I have a new egr valve, haven't replaced it yet.

anyway, this is an intermittant issue, no rhyme or reason to it. cold, hot, long drive, short, whatever, doesn't matter.

If I turn the engine off and restart, it will usually run fine again, although inevitably, it occurs again. could happen quickly, or two days down the road.

thoughts? thanks!