Well, from the dry and wet compression checks, I'd suspect burned valve(s) in number 3 cylinder. Kinda of interesting, because didn't the previous owner just have a head job done on that engine 3-4 months ago? Could be a coincidince, or perhaps the job was improperly done. Also, OEM spark plugs have only one ground electrode. Hhmmm .....

Yes, previous owner said he put on a new rebuilt head.

That why I was wondering what causes the burnt valves? Maybe there was an underlying issue that just burned the valves again, after the new head.

He gave me the old head and he supposedly "marked" the burnt valves.
And there was at least one burnt valve on every cylinder, more than one on some cylinders.

(Now I'm not sure if they actually were burnt, not sure how you tell, but that's just what he said)