2006 4.8is Rough Idle

[Baja_Bimmer]

My dad just got a 4.8is and it has an issue idling. We've unplugged the MAF, Valvetronic Servomotors, Valvetronic sensors, and VANOS solenoids, separately and in various combinations, with no change in idle characteristics.

Those characteristics being rough idle upon startup and it hovering around 1000 rpm while revving a few hundred RPM. It eventually smoothes out at 1500 RPM, and once the engine is at operating temp, idles normally. It also throws codes for misfires on every cylinder when cold. When revving it in any condition, it doesn't seem to misfire once above idle rpm.

We replaced the IVM and it had no affect on the idle issue. Today I hooked it up to ISTA+ and changed the minimum valve lift from 0.3mm to 0.8mm and that actually seemed to fix the high idle, but the engine now misfired on all cylinders while warm and cold, but did so consistently between those two conditions.

What do you guys think this could be? the previous owner said they did mist of the coils, all of the spark plugs, and filled it with gas. I don't believe it's the coils or gas, because it has two different brands of coils and all cylinders misfire the same, and I assume the knock sensors would take care of low octane gas causing this issue.