[Rustinmotion]

If your not using vacuum advance and you already confirmed with a strobe the max advance is being reached I don't think distributer is the cause, fuel starvation would show with lower max revs driving under load than revving it on the drive, coil has been swapped
Have you confirmed a healthy 12v it doesn't drop for some reason at 4k?
On all situations have you been using the same electrical ignition? If yes put the points back in to rule that out. Have you measured valve lift, are they opening to specification